用括号内所给动词的适当形式填空。

1. Look! Li Ping                (play) in the park.

2. Mrs Smith               (arrive) in Beijing yesterday.

3. My brother is a middle-school student. He               (go) to school early every day.

4. They               (visit) a factory tomorrow afternoon.

5. Mr Black               (not come). Let's wait for him at the gate.

6. A modern hospital               (build) in this city next year.

下列电器元件中，属于主令电器的是（）。

A.按钮

B.电极

C.接触器

D.接近开关

E.空气断路器