阅读下面短文, 掌握其大意, 然后从1—25各题所给的四个选项中, 选出一个 最佳答案。

　　 (A)　　

　　    There are 1 80 pyramids in Egypt. But the Great Pyramid is the biggest 2 . It is nearly 5000 years 3 . It is about 137 metres 4 today, but it was once higher. It is 5 2,300,000 6 stones. Most of them are higher than a man and weight about two and a half tons 7 . Some weight 8 fifteen tons. 9 took more than 100,000 men twenty 10 to build the Great Pyramid.　　

　　    Many cities today have problems. Some have too 11 people and cars. Some are full of 12 air. Some are too noisy. Scientists are 13 about ways to change cities. They want to make them better. One 14 is to build a dome (圆顶) over a 15 . Only offices, houses, hospitals and 16 would be under the dome. There would be no 17 in the city. This way the city would 18 get crowded (拥挤) or noisy. It would be 19 warm in winter and cool in summer. People would walk around 20 coats. No one would need a raincoat on a rainy day.

　　    Many people now think that teachers give students too many tests in class and too 21 homework after school. So, children do not have any 22 for other activities (活动). If teachers and parents pay enough attention to the problem, things would be 23 . Teachers should try to 24 the tests easier and give the students fewer exercises to do at home. Besides, parents should help their 25 to form good study habits (习惯).