Every object has weight. But the center of its weight is not always in the middle of the object. If the top of an object is heavier than its bottom, it will fall over easily. We say that its center of gravity is high. But if the bottom is heavier, it won’t fall easily. Then we say that its center of gravity is low.

Look at the first picture. This empty box must fall over, because its center of gravity (C) is not above the line of its bottom (AB).

Now look at the second picture. There is some heavy iron in the bottom of this box. It will not fall, because its center of gravity is above its bottom.

1.If the bottom of an object is ______ its top, it will fall over easily.

A. lighter than　　 B. heavier than　　 C. no heavier than　　  D. as heavy as

2.Please point out which box will not fall.

3.The main idea of the passage is _________.

A. why things fall over　　　　         B. a low center of gravity

C. a high center of gravity　　             D. that everything has weight

用所给单词的适当形式完成短文。（共10分，每小题1分）

There are lots of misunderstandings (误解) about Americans, and not just to do with money. Here are some of the most common ones:

All Americans are 　　56　 .

Like China, the US has big problems with poverty (贫穷). According to a report in 2011, almost half of all Americans are now 　　57　 poor or low-income (低收入). This is partly because the economic crisis (经济危机) makes many Americans lose 　　58　 .

All Americans like fast food.

Many Americans are confused when a Chinese friend 　　59　 them to McDonald’s or KFC. Chinese think that’s the kind of food Americans will 　　60　 . In fact, many Americans think this is junk food. They would rather 　　61　 a Chinese meal. In fact, there are lots of different kinds of restaurants in the US, including Chinese ones. Some Americans can 　　62　 use chopsticks!

All Americans own guns (枪).

This year, a lot more Americans own guns than before. Most gun 　　63　 live in certain parts of the US, like the South and Midwest, especially in rural areas. If you visit a city 　　64　 New York or San Francisco, don’t worry about 　　65　 shot; you’re not likely to meet anyone who owns a gun there.