阅读下列短文，从短文后各题所给的A、B、C、D四个选项中选出可以填入空白处的最佳选项。

There are many great jobs in the world. The people （1） do these jobs work hard to help us.

（2） know much about science. They use their knowledge to discover or create new things.

Engineers help build almost everything we use. Some engineers make TVs sound good. Some make robots （3） in our daily life. Some also make old things work well for people.

Police officers work hard to keep towns and cities safe. When accidents happen, they help people get out of danger. The police also try to stop accidents from happening. They make sure that people don’t （4） the law.

Cleaners pick up rubbish to keep our environment clean. They work day and night to keep us healthy, because we can get sick （5） germs（细菌）if rubbish is not picked up.

（1）

A．

who

B．

which

C．

whom

D．

whose

（2）

A．

Doctors

B．

Cooks

C．

Teachers

D．

Scientists

（3）

A．

thankful

B．

peaceful

C．

helpful

D．

careful

（4）

A．

break

B．

keep

C．

follow

D．

make

（5）

A．

to

B．

from

C．

at

D．

on