汽油极易挥发，在空气中的浓度达到（）mg/L，能引起人身中毒。
A.30～40
B.25～35
C.20～30
D.35～45
参考答案：A
根据句意和单词的首字母提示写单词。
1. This question is d_________. I can't answer it.
2. I have no brother or sister, b_________ I have many friends.
3. I like playing computer games.It's very i_________.
4. He has o_________ one pencil in his pencil case.
5. —Let's play soccer.—That sounds f_________.
因特网的主要功能是（）。
A．玩游戏
B．下载资料
C．传递营销信息
D．远程控制
