Một con lắc đơn dao động điều hòa tại nơi có gia tốc trọng trường g = π 2 m / s 2 . Chiều dài của dây treo con lắc là 25 cm thì tần số dao động là

A. 0,1 Hz

B. 10 Hz

C. 1 Hz

D. 100 Hz 

Trong các chất dưới đây, chất nào là amin bậc hai?

A.  H 2 N - CH 2 6 - NH 2

B.  CH 3 - NH - CH 2 CH 3

C.  CH 3 - CH NH 2 - CH 3

D.  CH 3 - N CH 3 - CH 2 CH 3

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.

Alexis de Tocqueville, the French political scientist, historian, philosopher and politician, is most famous for a four-volume book he wrote called “Democracy in America”. He came to America in 1831 to study the American form of democracy and what it might mean to the rest of the world. After a visit of only nine months, he wrote a remarkable book which is regarded as a classic. De Tocqueville had unusual powers of observation. He described not only the democratic system of government and how it operated, but also its effect on how Americans think, feel, and act. Many scholars believe he had a deeper understanding of traditional American beliefs and values than anyone else who has written about the United States. What is so remarkable is that many of these traits which he observed nearly 200 years ago, are still visible and meaningful today. His observations are also important because the timing of his visit, the 1830s, was before America was industrialized. This was the era of the small farmer, the small businessman, and the settling of the western frontier. It was the period of history when the traditional values of the new country were newly established. In just a generation, some 40 years since the adoption of the U.S. Constitution, the new form of government had already produced a society of people with unique values. He was, however, a neutral observer and saw both the good and bad sides of these qualities.

The first part of “Democracy in America” was written in 1831-32 and published in 1835. A highly positive and optimistic account of American government and society, the book was very well received. He attempted to get a glimpse of the essence of American society, all the while promoting his own philosophy: the equaling of the classes and the inevitable depth of aristocratic privilege. The rest of the book he labored on for four years, and in 1840 the second part was published. This was substantially more pessimistic than the first, warning of the dangers despotism and governmental centralization, and applying his ideas and criticisms more directly to France. As a result, it was not received as well as the first part, except in England where it was acclaimed highly.

Question:What in the passage is mentioned as being truly remarkable?

A.  the book was so detailed and thorough after only such a comparatively short visit.

B.  de Tocqueville’s powers of observation.

C.  many of his observations are still visible and meaningful today.

D.  that the second volume should be so pessimistic in comparison with the first.

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 28 to 34.

   For more than six million American children, coming home after school means coming back to an empty house. Some deal with the situation by watching TV. Some may hide. But all of them have something in common. They spend part of each day alone. They are called “latchkey children”. They are children who look after themselves while their parents work. And their bad condition has become a subject of concern.

   Lynette Long was once the principal of an elementary school. She said, “we had a school rule against wearing jewelry. A lot of kids had chains around their necks with keys attached. I was constantly telling them to put the keys inside shirts. There were so many keys; it never came to my mind what they meant.” Slowly, she learned that they were house keys.

   She and her husband began talking to the children who had keys. They learned of the effect working couples and single parents were having on their children. Fear was the biggest problem faced by children at home alone. One in three latchkey children the Longs talked to reported beinu frightened. Many had nightmares and were worried about their own safety

   The most common way latchkey children deal with their fears is by hiding. They mav hide in a shower stall, under a bed or in a closet. The second is TV. They often turn the volume up It's hard to get statistics on latchkey children, the Longs have learned. Most parents are slow to admit that they leave their children alone.

It’s difficult to find out the number of latchkey children because _____________ .

A. there are too many of them in the whole country

B. most parents are reluctant to admit that they leave their children alone

C. they hide themselves in shower stalls or under beds

D. they do not give information about themselves for safety reasons

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 35 to 42.

  What geologists call the Basin and Range Province in the United States roughly coincides in its northern portions with the geographic province known as the Great Basin. The Great Basin is surrounded on the west by the Sierra Nevada and on the east by the Rocky Mountains; it has no outlet to the sea. The prevailing winds in the Great Basin are from the west. Warm, moist air from the Pacific Ocean is forced upward as it crosses the Sierra Nevada. At the higher altitudes it cools and the moisture it carries is precipitated as rain or snow on the western slopes of the mountains. That which reaches the Basin is air wrung dry of moisture. What little water falls there as rain or snow, mostly in the winter months, evaporates on the broad, flat desert floors. It is, therefore, an environment in which organism battle for survival. Along the rare watercourses, cottonwoods and willows eke out a sparse existence. In the upland ranges, pinion pines and junipers struggle to hold their own.

  But the Great Basin has not always been so arid. Many of its dry, closed depressions were once filled with water. Owens Valley, Panamint Valley, and Death Valley were once a string of interconnected lakes. The two largest of the ancient lakes of the Great Britain were Lake Lahontan and Lake Bonneville. The Great Salt Lake is all that remains of the latter, and Pyramid Lake is one of the last briny remnants of the former.

  There seem to have been several periods within the last tens of thousands of years when water accumulated in these basins. The rise and fall of the lakes were undoubtedly linked to the advances and retreats of the great ice sheets that covered much of the northern part of the North American continent during those times. Climatic changes during the Ice Ages sometimes brought cooler, wetter weather to mid-latitude deserts worldwide, including those of the Great Basin. The broken valleys of the Great Basin provided ready receptacles for this moisture.

According to the passage, the Ice Ages often brought about _____________

A. wetter weather

B. warmer climates

C. broken valley

D. desert formation

Ý nào không đúng với sinh đẻ có kế hoạch?

A. Điều chỉnh khoảng cách sinh con        

B. Điều chỉnh sinh con trai hay con gái

C. Điều chỉnh thời điểm sinh con      

D. Điều chỉnh về số con

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 23 to 27. Fill in the appropriate word in question 27

        Easter is a holiday in late March or early April, the first Sunday after the first full moon after 21 March. Many people (23) _________it with their family or have a short holiday/ vacation. It is also an important Christian festival. Easter Sunday, the day of the Resurrection, is the end of Lent (24) _________ the most important date in the Christian year. Many people who do not go to church at other times go on Easter Sunday. It was once common for people to wear new clothes to church on this day. Women wore new hats, called Easter bonnets. Today, people sometimes make elaborately decorated Easter bonnets for fun. A few people send Easter cards with religious symbols on them or pictures of small chickens, lambs, rabbits and spring flowers, all traditionally associated (25)          _________ Easter.

        The Friday before Easter Sunday is called Good Friday and is (26) _________ as the day Christ was crucified (= hanged on a cross to die). On Good Friday many people eat hot cross buns (= fruit buns decorated with a simple cross). The Monday after Easter is called Easter Monday. In Britain Good Friday and Easter Monday are both bank holidays. In the US, each company decides for itself (27) _________to close or remain open on those days.

A. if

B. how

C. why

D. whether