---What attracts people to California is its pleasant climate and relaxed lifestyle.

---This is ____ each year a great number of people from all over the world try to ____ to California.

A．how; immigrate

B．Why; immigrate

C．because; remove

D．why; remove

汽动给水泵汽化的现象有（）。

A、前置泵电流摆动；

B、给水泵出口压力下降且摆动；

C、给水流量下降且摆动；

D、泵内有噪音及水击声，泵组振动增大。