成语“杞人忧天”常比喻不必要的或缺乏根据的忧虑和担心。但在地球生态环境问题日益严

点燃的蜡烛放在正在发声的扬声器前，烛焰会随之摇曳，这是因为______________。

根据上下文补全对话。

A: Excuse me, __1__ I ask you some questions?

B: __2__ .

A: When __3__ you born?

B: In March, 1983.

A: You're 15 years old, right? Only one year __4__ than me. I am 14.

B: But you look much __5__  than me.

A : Really?  Thank you. And how __6__ have you been in China?

B: About 3 years. We moved here __7__ my father likes working in China.

A: __8__ do you like here?

B: Very much. I like the people __9__ the food here. The people are very friendly __10__ us.

我国西部的陆上邻国有（）。(五级、四级)

A、巴基斯坦 

B、阿富汗 

C、哈萨克斯坦 

D、塔吉克斯坦

三类防雷建筑物，冲击接地电阻不宜大于（）。

A.5

B.10

C.20

D.30