完成句子。
1. It's not just because they ____（不能理解它是什么意思）.
2. F 2 F ____ （表示面对面）.
3. Homophone often use letters and numbers that ____（听起来像单词或单词的一部分）.
4. I don't think twelve-year-olds should be allowed to ____ （穿耳洞）.
5. I think teenagers should be allowed to____（与朋友们外出）.
6. If we can't wear our own clothes, we should be allowed to____ （设计自己的校服）.
7. I get nervous before big parties and then I ____（出皮疹）.
8. It isn't good to borrow your friends' books ____ （未经允许）.
 9. My life ____（有了很大的改变）in the last few years.

一条染色体上有____个DNA分子，一个DNA分子上含有____个基因．

请用所学物理知识解释“只闻其声不见其人”这种现象？

对下面几句诗的韵脚判断正确的一项是（      ）。

僵卧孤村不自哀，尚思为国戍轮台。

夜阑卧听风吹雨，铁马冰河入梦来。