用所给单词的适当形式填空。

1. My brother's _____ (write) habits are not good.

2. Some boys play football two or three _____ (time) a week.

3. I _____ (not think) so.

4. My mother _____ (have) a healthy lifestyle.

   She eats _____ (little) junk food but more vegetables.

5. You should _____ (help) each other.

用尾纤进行光口自环时，应在收发光口间加装（），保证光口收光功率在该光板的允许接收光功率范围以内，大于接收灵敏度，小于过载光功率。

A、光分路器

B、光合路器

C、光衰减器

D、光功率计