5. The Great Wall is a great man-made P.

4. The Sahara is the biggest d in the world.

3. The a emperor built the Great Wall to protect his country.

2. The Caspian Sea is a s lake.

Ⅱ.根据句意及首字母提不完成下列句子.

1. As you can s ，several big changes have taken place.

7. The (主要的) reason is that he is lost in a big city.

6. At that time,jeans are the most (流行) clothes.

5. We should do something to (保护) the environment.

4. China is famous for the (长城) .

3. China has the biggest (人口) in the world.