Hệ bất phương trình $\left\{\begin{array}{l}{\mathrm{x}}^2 - 4 < \mathrm{x} + 2\\ \mathrm{x} + 2 \le 0\end{array}\right.$ có tập nghiệm là:

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

All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals-- whether marsupials, platypuses, spiny anteaters, or placental mammals -- have in common.

For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them an edge in their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size that it is better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young are shielded against the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.

Question: The word "tend" in the second paragraph is closest in meaning to _______.         

Phát biểu nào sau đây về dao động tắt dần là sai?  

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

All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals - whether marsupials, platypuses, spiny anteaters, or placental mammals - have in common.

For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them an edge in their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size that it is better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young are shielded against the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.

Question: The word "edge" in the third paragraph is closest in meaning to _______.         

Khi nói về dao động cưỡng bức, phát biểu nào sau đây là đúng?  

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

All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive system. It is a nonelective part of parental care and the defining feature of a mammal, the most important thing that mammals - whether marsupials, platypuses, spiny anteaters, or placental mammals - have in common.

For animals other than mammals, then, feeding is not intrinsic to parental care. Animals add it to their reproductive strategies to give them an edge in their lifelong quest for descendants. The most vulnerable moment in any animal's life is when it first finds itself completely on its own, when it must forage and fend for itself. Feeding postpones that moment until a young animal has grown to such a size that it is better able to cope. Young that are fed by their parents become nutritionally independent at a much greater fraction of their full adult size. And in the meantime those young are shielded against the vagaries of fluctuating of difficult-to-find supplies. Once a species does take the step of feeding its young, the young become totally dependent on the extra effort. If both parents are removed, the young generally do not survive.

Question: According to the passage, how do some insects make sure their young have food?         

Một vật dao động cưởng bức dưới tác dụng của ngoại lực F = F₀ cos(0,5πft) (với F₀ và f không đổi. t tính bằng s). Tần số của dao động cưỡng bức của vật là ?         

Chọn đáp án sai khi nói về dao động cưỡng bức:

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:

                                                        ACADEMICS AREN’T THE PROBLEM

Studies about how students use their time might shed light on whether they face increased academic and financial pressures compared with earlier eras.

Based on data about how students are spending time, academic or financial pressures don’t seem to be greater now than a generation ago.

The data show that full-time students in all types of colleges study much less now than they did a generation ago - a full 10 hours a week less. Students are also receiving significantly higher grades. So it appears that academic pressures are, in fact, considerably lower than they used to be.

The time-use data don’t suggest that students feel greater financial pressures, either. When the time savings and lower opportunity costs are factored in, college appears less expensive for most students than it was in the 1960s. And though there are now full-time students working to pay while in college, they study less even when paid work choices are held constantly.

In other words, full-time students do not appear to be studying less in order to work more. They appear to be studying less and spending the extra time on leisure activities or fun. It seems hard to imagine that students feeling increased financial pressures would respond by taking more leisure.
   

Based on how students are spending their time then, it doesn’t look as though academic or financial pressures are greater now than a generation ago. The time-use data don’t speak directly to social pressures, and it may well be that these have become more intense lately.

In one recent set of data, students reported spending more than 23 hours per week either socializing with friends or playing on the computer for fun. Social activities, in person or on computer, would seem to have become the major focus of campus life. It is hard to tell what kinds of pressures would be associated with this change.

Question: Students get higher grades as _______.         

Dao động tắt dần là một dao động có:  

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:

                                                        ACADEMICS AREN’T THE PROBLEM

Studies about how students use their time might shed light on whether they face increased academic and financial pressures compared with earlier eras.

Based on data about how students are spending time, academic or financial pressures don’t seem to be greater now than a generation ago.

The data show that full-time students in all types of colleges study much less now than they did a generation ago - a full 10 hours a week less. Students are also receiving significantly higher grades. So it appears that academic pressures are, in fact, considerably lower than they used to be.

The time-use data don’t suggest that students feel greater financial pressures, either. When the time savings and lower opportunity costs are factored in, college appears less expensive for most students than it was in the 1960s. And though there are now full-time students working to pay while in college, they study less even when paid work choices are held constantly.

In other words, full-time students do not appear to be studying less in order to work more. They appear to be studying less and spending the extra time on leisure activities or fun. It seems hard to imagine that students feeling increased financial pressures would respond by taking more leisure.
   

Based on how students are spending their time then, it doesn’t look as though academic or financial pressures are greater now than a generation ago. The time-use data don’t speak directly to social pressures, and it may well be that these have become more intense lately.

In one recent set of data, students reported spending more than 23 hours per week either socializing with friends or playing on the computer for fun. Social activities, in person or on computer, would seem to have become the major focus of campus life. It is hard to tell what kinds of pressures would be associated with this change.

Question: The study's conclusion that students' workload now is not greater than before is based on _______.