---Tom is so worried about the test that he said he was going to study all night.

----Tell him he should quit _________and get some help. 

A．to have worried

B．to worry

C．worring

D．from worrying

采用中间电位作业时，屏蔽服所起的主要作用是（）。

A.屏蔽高压电场、分流高频电流；

B.屏蔽电场；

C.分流静电感应电击电流；

D.与带电部分隔离。