考考你的记忆力，根据句意及首字母补全在本课中出现的单词。

1.We are d_____ from them.

2."R_____"means  "again".

3.Can you s_____ the song in English?

4.I hope you r_____ to tell him about it.

5.Do you have a s_____ friend?

6.I'm good at ping-pong. That makes me u_____.

7.Can you write a letter to me to d_____ yourself?

8.Let me i_____ my friend to you.

9.Do you know how they c_____ the festival?

10.We should be c_____ in ourselves.

新物种形成最显著的标志是（）

A.具有一定的形态结构

B.具有一定的生理功能

C.产生了生殖隔离

D.改变了基因频率