按容器承受压力时所处的应力状态，压力容器可分为（）
A、薄壁容器
B、中壁容器
C、厚壁容器
D、超厚壁容器
参考答案：A, C
用括号内所给词的适当形式填空。
1. My brother _____ (have)a baseball.
2. _____ he _____ (play) sports every day?
3. She ______ ( not watch) TV in the evening.
4. Let's ______ (take) these books to the classroom.
5. Can you ______ ( bring) the pen to me?
6. We have many ______ ( sport) clubs.
7. He only watches ______ ( they) on TV.
8. I have only one ______ ( watch).
9. Let ______ ( I ) have a look.
10. Tom ______ ( not do) sports in the morning.
人口在国家内部的空间移动包括地（）（）和城市间迁移。
