Trong sơ đồ khối của một máy thu sóng vô tuyến đơn giản không có bộ phận nào dưới đây?

A. Biến điệu

B. Thu sóng

C. Khuếch đại

D. Tách sóng

Công thức tính chu kì dao động điều hòa của con lắc đơn có chiều dài l tại nơi có gia tốc trọng trường g là:

A.  T = 2 π k m

B.  T = 2 π g l

C.  T = 2 π m k

D.  T = 2 π l g

Trong sóng điện từ, dao động của điện trường và của từ trường tại một điểm luôn

A. ngược pha nhau

B. lệch pha nhau  π 4

C. cùng pha nhau

D. lệch pha nhau π 2

TV advertising in the late afternoon tends to _______ young children. 

A. aim 

B. point 

C. focus 

D. target 

I don’t feel like buying a _______ in a poke; we’d better check the content. 

A. ox 

B. pig 

C. buffalo 

D. cattle 

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

Certainly no creature in the sea is odder than the common sea cucumber. All living creature, especially human beings, have their peculiarities, but everything about the little sea cucumber seems unusual. What else can be said about a bizarre animal that, among other eccentricities, eats mud, feeds almost continuously day and night but can live without eating for long periods, and can be poisonous but is considered supremely edible by gourmets?

For some fifty million years, despite all its eccentricities, the sea cucumber has subsisted on its diet of mud. It is adaptable enough to live attached to rocks by its tube feet, under rocks in shallow water, or on the surface of mud flats. Common in cool water on both Atlantic and Pacific shores, it has the ability to such up mud or sand and digest whatever nutrients are present.

Sea cucumbers come in a variety of colors, ranging from black to reddish-brown to sand-color and nearly white. One form even has vivid purple tentacle. Usually the creatures are cucumber-shaped-hence their name-and because they are typically rock inhabitants, this shape, combine with flexibility, enables them to squeeze into crevices where they are safe from predators and ocean currents.

Although they have voracious appetites, eating day and night, sea cucumbers have the capacity to become quiescent and live at a low metabolic rate-feeding sparingly or not at all for long periods, so that the marine organisms that provide their food have a chance to multiply. If it were not for this faculty, they would devour all the food available in a short time and would probably starve themselves out of existence.

But the most spectacular thing about the sea cucumber is the way it defends itself. Its major enemies are fish and crabs, when attacked, it squirts all its internal organs into the water. It also casts off attached structures such as tentacles. The sea cucumber will eviscerate and regenerate itself if it is attached or even touched; it will do the same if the surrounding water temperature is too high or if the water becomes too polluted.
Question:The words “this faculty” refers to the sea cucumber’s ability to

A. live at a low metabolic rate

B. squeeze into crevices

C. devour all available food in a short time

D. suck up mud or sand

Những người sản xuất kinh doanh đua nhau cải tiến máy móc hiện đại và nâng cao trình độ chuyên môn cho người lao động là thể hiện mặt tích cực nào dưới đây của cạnh tranh?

A. Kích thích lực lượng sản xuất phát triển, năng suất lao động tăng lên.

B. Khai thác tối đa mọi nguồn lực của đất nước.

C. Thúc đẩy tăng trưởng kinh tế, hội nhập kinh tế quốc tế.

D. Góp phần ổn định thị trường hàng hóa

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 43 to 50.

    After the United States purchased Louisiana from France and made it their newest territory in 1803, President Thomas Jefferson called for an expedition to investigate the land the United States had bought for $15 million. Jefferson’s secretary, Meriwether Lewis, a woodsman and a hunter from childhood, persuaded the president to let him lead this expedition. Lewis recruited Army officer William Clark to be his co-commander. The Lewis and Clark expedition led the two young explorers to discover a new natural wealth of variety and abundance about which they would return to tell the world.

    When Lewis and Clark departed from St. Louis in 1804, they had twenty-nine in their party, including a few Frenchmen and several men from Kentucky who were well-known frontiersmen. Along the way, they picked up an interpreter named Toussant Charbonneau and his Native American wife, Sacajawea, the Shoshoni “Bird Woman” who aided them as guide and peacemaker and later became an American legend.

    The expedition followed the Missouri River to its source, made a long portage overland though the Rocky Mountains, and descended the Columbia River to the Pacific Ocean. On the journey, they encountered peaceful Otos, whom they befriended, and hostile Teton Sioux, who demanded tribute from all traders. They also met Shoshoni, who welcomed their little sister Sacajawea, who had been abducted as a child by the Mandans. They discovered a paradise full of giant buffalo herds and elk and antelope so innocent of human contact that they tamely approached the men. The explorers also found a hell blighted by mosquitoes and winters harsher than anyone could reasonably hope to survive. They became desperately lost, then found their way again. Lewis and Clark kept detailed journals of the expedition, cataloging a dazzling array of new plants and animals, and even unearthing the bones of a forty-five-foot dinosaur.

          When the party returned to St. Louis in 1806 after travelling almost 8,000 miles, they were eagerly greeted and grandly entertained. Their glowing descriptions of this vast new West provided a boon to the westward migration now becoming a permanent part of American life. The journals written by Lewis and Clark are still widely read today

The purpose of the Lewis and Clark expedition was ______.

A. to establish trade with the Otos and Teton Sioux

B. to explore territory purchased by the United States

C. to purchase land from France

D. to find the source of the Missouri River

Có:2^3=8,3^2=9.

=> Có:2^3^8 va3^2^9