Ở một loài động vật, màu sắc lông do một gen có hai a;en quy định,  lông vàng và kiểu aa quy định lông trắng. Cho các trường hợp sau:

(1) Các cá thể lông xám có sức sống và khả năng sinh sản kém, các cá thể khác có sức sống và khả năng sinh sản bình thường.

(2) Các cá thể lông vàng có sức sống và khả năng sinh sản kém, các cá thể khác có sức sống và khả năng sinh sản bình thường.

(3) Các cá thể lông trắng có sức sống và khả năng sinh sản kém, các cá thể khác có sức sống và khả năng sinh sản bình thường.

(4) Các cá thể lông trắng và các cá thể lông xám đều có sức sống và khả năng sinh sản kém như nhau các cá thể lông vàng có sức sống và khả năng sinh sản bình thường. Giả sử một quần thể thuộc loài này có thành phần kiểu gen là:. Chọn lọc tự nhiên sẽ nhanh chóng làm thay đổi tần số alen của quần thể trong các trường hợp:             

Question 34: 

A tiny village school is soon to celebrate its 110 birthday - against all expectations. Five years ago it seemed certain to close but parents and other villagers fought the local education authority and raised funds to keep it (31)_______. It is now ending its first term as a school (32)_____by the village community and the villagers are just proud of their achievement. They were furious when education chiefs tried to make them send the village children to other schools further away because the number of pupils at the village school was too (33)_____. The villagers started a huge campaign to (34) _____money. They collected enough to hire a teacher and begin to help with school cleaning, lunch supervision and lessons. Now the school is doing well and it seems (35)____ it will continue to run in the future. 

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 40:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 39:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 38:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 37:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 36:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 20:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 21:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 17:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 18: