用所给单词的适当形式填空。

1. Don't spend much energy _____ (make) others happy.

2. Why do many parents keep their children from _____ (go) out after school ?

3. It's necessary _____ ( keep) our classroom tidy and clean.

4. He pretended _____ (is) friendly with me.    .

5. I thanked them for their _____ ( kind) they showed me.

在单盘测试中，（）不属于光特性测试。

A.单盘光缆长度测试

B.单盘光缆的后项散射曲线测试

C.中继段衰减测试

D.单盘光缆的折射率测试