Trong không gian với hệ tọa độ Oxyz cho . Viết phương trình mặt phẳng (P) đi qua A, B và (P) tạo với mp(Oyz) góc a thỏa mãn ?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

Dodder is an unusual and unwanted plant that attacks other plants. Except for its flowers, the plant looks like spaghetti noodles. Its almost leafless, thread–like stems hang down atop other plants that dodder needs to stay alive. Dodder does not produce its own food. Instead, it steals it from other plants. It feeds by sucking juices from the plant it is wrapped around, often making its host very weak or even killing it.

Dodder can find other plants by their smell. When a dodder seedling starts growing, it follows the scent of plants it prefers, like tomato plants, potato plants, or other farm crops. Unlike most plants that usually grow in the direction of light or warmth, a dodder plant will grow in the direction of, for example, tomato odor––if a tomato happens to be growing nearby.

However, a young dodder plant must find a host plant quickly. If it cannot catch a whiff of a potential host within a few days, it will dry up and disappear—even if there is plenty of water around. Once it finds a host, the young dodder plant will attach itself to it and start growing faster. At that point, the dodder plant will drop its root.

Dodder is thus a difficult weed to manage and a real headache for farmers. When it does get out of hand, dodder can greatly reduce a farmer’s harvest or even destroy crops completely. Before sowing their produce, farmers in warm parts of the world often check to make sure no unwanted dodder seeds have intermingled with their crop seeds. This is a good way to stop dodder plants from sneaking their way into a crop field.

Question: What causes dodder to grow in a particular direction?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

Dodder is an unusual and unwanted plant that attacks other plants. Except for its flowers, the plant looks like spaghetti noodles. Its almost leafless, thread–like stems hang down atop other plants that dodder needs to stay alive. Dodder does not produce its own food. Instead, it steals it from other plants. It feeds by sucking juices from the plant it is wrapped around, often making its host very weak or even killing it.

Dodder can find other plants by their smell. When a dodder seedling starts growing, it follows the scent of plants it prefers, like tomato plants, potato plants, or other farm crops. Unlike most plants that usually grow in the direction of light or warmth, a dodder plant will grow in the direction of, for example, tomato odor––if a tomato happens to be growing nearby.

However, a young dodder plant must find a host plant quickly. If it cannot catch a whiff of a potential host within a few days, it will dry up and disappear—even if there is plenty of water around. Once it finds a host, the young dodder plant will attach itself to it and start growing faster. At that point, the dodder plant will drop its root.

Dodder is thus a difficult weed to manage and a real headache for farmers. When it does get out of hand, dodder can greatly reduce a farmer’s harvest or even destroy crops completely. Before sowing their produce, farmers in warm parts of the world often check to make sure no unwanted dodder seeds have intermingled with their crop seeds. This is a good way to stop dodder plants from sneaking their way into a crop field.

Question: The expression catch a whiff is closest in meaning to________.             

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

Dodder is an unusual and unwanted plant that attacks other plants. Except for its flowers, the plant looks like spaghetti noodles. Its almost leafless, thread–like stems hang down atop other plants that dodder needs to stay alive. Dodder does not produce its own food. Instead, it steals it from other plants. It feeds by sucking juices from the plant it is wrapped around, often making its host very weak or even killing it.

Dodder can find other plants by their smell. When a dodder seedling starts growing, it follows the scent of plants it prefers, like tomato plants, potato plants, or other farm crops. Unlike most plants that usually grow in the direction of light or warmth, a dodder plant will grow in the direction of, for example, tomato odor––if a tomato happens to be growing nearby.

However, a young dodder plant must find a host plant quickly. If it cannot catch a whiff of a potential host within a few days, it will dry up and disappear—even if there is plenty of water around. Once it finds a host, the young dodder plant will attach itself to it and start growing faster. At that point, the dodder plant will drop its root.

Dodder is thus a difficult weed to manage and a real headache for farmers. When it does get out of hand, dodder can greatly reduce a farmer’s harvest or even destroy crops completely. Before sowing their produce, farmers in warm parts of the world often check to make sure no unwanted dodder seeds have intermingled with their crop seeds. This is a good way to stop dodder plants from sneaking their way into a crop field.

Question: What will happen if a dodder plant starts growing where there are no other plants around?         

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions:

Dodder is an unusual and unwanted plant that attacks other plants. Except for its flowers, the plant looks like spaghetti noodles. Its almost leafless, thread–like stems hang down atop other plants that dodder needs to stay alive. Dodder does not produce its own food. Instead, it steals it from other plants. It feeds by sucking juices from the plant it is wrapped around, often making its host very weak or even killing it.

Dodder can find other plants by their smell. When a dodder seedling starts growing, it follows the scent of plants it prefers, like tomato plants, potato plants, or other farm crops. Unlike most plants that usually grow in the direction of light or warmth, a dodder plant will grow in the direction of, for example, tomato odor––if a tomato happens to be growing nearby.

However, a young dodder plant must find a host plant quickly. If it cannot catch a whiff of a potential host within a few days, it will dry up and disappear—even if there is plenty of water around. Once it finds a host, the young dodder plant will attach itself to it and start growing faster. At that point, the dodder plant will drop its root.

Dodder is thus a difficult weed to manage and a real headache for farmers. When it does get out of hand, dodder can greatly reduce a farmer’s harvest or even destroy crops completely. Before sowing their produce, farmers in warm parts of the world often check to make sure no unwanted dodder seeds have intermingled with their crop seeds. This is a good way to stop dodder plants from sneaking their way into a crop field.  

Question: The expression get out of hand is closest in meaning to_________.         

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions below:

 Birds that feed in flocks commonly retire together into roosts. The reasons for roosting communally are not always obvious, but there are some likely benefits. In winter especially, it is important for birds to keep warm at night and conserve precious food reserves. One way to do this is to find a sheltered roost. Solitary roosters shelter in dense vegetation or enter a cavity - horned larks dig holes in the ground and ptarmigan burrow into snow banks - but the effect of sheltering is magnified by several birds huddling together in the roosts, as wrens, swifts, brown creepers, bluebirds, and anis do. Body contact reduces the surface area exposed to the cold air, so the birds keep each other warm. Two kinglets huddling together were found to reduce their heat losses by a quarter, and three together saved a third of their heat.

 The second possible benefit of communal roosts is that they act as “information centers”. During the day, parties of birds will have spread out to forage over a very large area. When they return in the evening some will have fed well, but others may have found little to eat. Some investigators have observed that when the birds set out again next morning, those birds that did not feed well on the previous day appear to follow those that did. The behavior of common and lesser kestrels may illustrate different feeding behaviors of similar birds with different roosting habits. The common kestrel hunts vertebrate animals in a small, familiar hunting ground, whereas the very similar lesser kestrel feeds on insects over a large area. The common kestrel roosts and hunts alone, but the lesser kestrel roosts and hunts in flocks, possibly so one bird can learn from others where to find insect swarms.

 Finally, there is safety in numbers at communal roosts since there will always be a few birds awake at any given moment to give the alarm. But this increased protection is partially counteracted by the fact that mass roosts attract predators and are especially vulnerable if they are on the ground. Even those in trees can be attacked by birds of prey. The birds on the edge are at greatest risk since predators find it easier to catch small birds perching at the margins of the roost.

Question 43: The word “they” in paragraph 3 refers to _______.         

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 41 to 50:

Until recently, most American entrepreneurs were men. Discrimination against women in business, the demands of caring for families, and lack of business training had kept the number of women entrepreneurs small. Now, however, businesses owned by women account for more than $40 billion in annual revenues, and this figure is likely to continue rising throughout the 1990s. As Carolyn Doppelt Gray, an official of the Small Business Administration, has noted, "The 1970s was the decade of women entering management, and the 1980s turned out to be the decade of the woman entrepreneur". What are some of the factors behind this trend? For one thing, as more women earn advanced degrees in business and enter the corporateworld, they are finding obstacles. Women are still excluded from most executive suites. Charlotte Taylor, a management consultant, had noted, "In the 1970s women believed if they got an MBA and worked hard they could become chairman of the board. Now they've found out that isn't going to happen, so they go out on their own". In the past, most women entrepreneurs worked in "women's" fields: cosmetics and clothing, for example. But this is changing. Consider ASK Computer Systems, a $22-million-a-year computer software business. It was founded in 1973 by Sandra Kurtzig, who was then a housewife with degrees in math and engineering. When Kurtzig founded the business, her first product was software that let weekly newspapers keep tabs on their newspaper carriers and her office was a bedroom at home, with a shoebox under the bed to hold the company's cash. After she succeeded with the newspaper software system, she hired several bright computer-science graduates to develop additional programs. When these were marketed and sold, ASK began to grow. It now has 200 employees, and Sandra Kurtzig owns $66.9 million of stock. Of course, many women who start their own businesses fail, just as men often do. They still face hurdles in the business world, especially problems in raising money; the banking and finance world is still dominated by men, and old attitudes die hard. Most businesses owned by women are still quite small. But the situation is changing; there are likely to be many more Sandra Kurtzigs in the years ahead.  

Question 48: The word “hurdles” in the passage can be best replaced by _________.           

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 41 to 50:

Until recently, most American entrepreneurs were men. Discrimination against women in business, the demands of caring for families, and lack of business training had kept the number of women entrepreneurs small. Now, however, businesses owned by women account for more than $40 billion in annual revenues, and this figure is likely to continue rising throughout the 1990s. As Carolyn Doppelt Gray, an official of the Small Business Administration, has noted, "The 1970s was the decade of women entering management, and the 1980s turned out to be the decade of the woman entrepreneur". What are some of the factors behind this trend? For one thing, as more women earn advanced degrees in business and enter the corporateworld, they are finding obstacles. Women are still excluded from most executive suites. Charlotte Taylor, a management consultant, had noted, "In the 1970s women believed if they got an MBA and worked hard they could become chairman of the board. Now they've found out that isn't going to happen, so they go out on their own". In the past, most women entrepreneurs worked in "women's" fields: cosmetics and clothing, for example. But this is changing. Consider ASK Computer Systems, a $22-million-a-year computer software business. It was founded in 1973 by Sandra Kurtzig, who was then a housewife with degrees in math and engineering. When Kurtzig founded the business, her first product was software that let weekly newspapers keep tabs on their newspaper carriers and her office was a bedroom at home, with a shoebox under the bed to hold the company's cash. After she succeeded with the newspaper software system, she hired several bright computer-science graduates to develop additional programs. When these were marketed and sold, ASK began to grow. It now has 200 employees, and Sandra Kurtzig owns $66.9 million of stock. Of course, many women who start their own businesses fail, just as men often do. They still face hurdles in the business world, especially problems in raising money; the banking and finance world is still dominated by men, and old attitudes die hard. Most businesses owned by women are still quite small. But the situation is changing; there are likely to be many more Sandra Kurtzigs in the years ahead.  

Question 47: The expression “keep tabs on” in the passage is closest meaning to _________.         

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 41 to 50:

Until recently, most American entrepreneurs were men. Discrimination against women in business, the demands of caring for families, and lack of business training had kept the number of women entrepreneurs small. Now, however, businesses owned by women account for more than $40 billion in annual revenues, and this figure is likely to continue rising throughout the 1990s. As Carolyn Doppelt Gray, an official of the Small Business Administration, has noted, "The 1970s was the decade of women entering management, and the 1980s turned out to be the decade of the woman entrepreneur". What are some of the factors behind this trend? For one thing, as more women earn advanced degrees in business and enter the corporateworld, they are finding obstacles. Women are still excluded from most executive suites. Charlotte Taylor, a management consultant, had noted, "In the 1970s women believed if they got an MBA and worked hard they could become chairman of the board. Now they've found out that isn't going to happen, so they go out on their own". In the past, most women entrepreneurs worked in "women's" fields: cosmetics and clothing, for example. But this is changing. Consider ASK Computer Systems, a $22-million-a-year computer software business. It was founded in 1973 by Sandra Kurtzig, who was then a housewife with degrees in math and engineering. When Kurtzig founded the business, her first product was software that let weekly newspapers keep tabs on their newspaper carriers and her office was a bedroom at home, with a shoebox under the bed to hold the company's cash. After she succeeded with the newspaper software system, she hired several bright computer-science graduates to develop additional programs. When these were marketed and sold, ASK began to grow. It now has 200 employees, and Sandra Kurtzig owns $66.9 million of stock. Of course, many women who start their own businesses fail, just as men often do. They still face hurdles in the business world, especially problems in raising money; the banking and finance world is still dominated by men, and old attitudes die hard. Most businesses owned by women are still quite small. But the situation is changing; there are likely to be many more Sandra Kurtzigs in the years ahead.  

Question 50: The author’s attitude about the future of women in business is_________.         

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 41 to 50:

Until recently, most American entrepreneurs were men. Discrimination against women in business, the demands of caring for families, and lack of business training had kept the number of women entrepreneurs small. Now, however, businesses owned by women account for more than $40 billion in annual revenues, and this figure is likely to continue rising throughout the 1990s. As Carolyn Doppelt Gray, an official of the Small Business Administration, has noted, "The 1970s was the decade of women entering management, and the 1980s turned out to be the decade of the woman entrepreneur". What are some of the factors behind this trend? For one thing, as more women earn advanced degrees in business and enter the corporateworld, they are finding obstacles. Women are still excluded from most executive suites. Charlotte Taylor, a management consultant, had noted, "In the 1970s women believed if they got an MBA and worked hard they could become chairman of the board. Now they've found out that isn't going to happen, so they go out on their own". In the past, most women entrepreneurs worked in "women's" fields: cosmetics and clothing, for example. But this is changing. Consider ASK Computer Systems, a $22-million-a-year computer software business. It was founded in 1973 by Sandra Kurtzig, who was then a housewife with degrees in math and engineering. When Kurtzig founded the business, her first product was software that let weekly newspapers keep tabs on their newspaper carriers and her office was a bedroom at home, with a shoebox under the bed to hold the company's cash. After she succeeded with the newspaper software system, she hired several bright computer-science graduates to develop additional programs. When these were marketed and sold, ASK began to grow. It now has 200 employees, and Sandra Kurtzig owns $66.9 million of stock. Of course, many women who start their own businesses fail, just as men often do. They still face hurdles in the business world, especially problems in raising money; the banking and finance world is still dominated by men, and old attitudes die hard. Most businesses owned by women are still quite small. But the situation is changing; there are likely to be many more Sandra Kurtzigs in the years ahead.  

Question 49: It can be inferred from the passage that the author believes that business operated by women are small because_________.