--Can thinking about yourself too much make you sick?

--I think so. It is reported that        people talk about themselves much more than        people.

A. nondepressed, depressed

B. depressed, nondepressed

C. depressive, depressed

下列选项中，属于蒸汽往复泵抽空的原因的是（）。

A、液缸套损坏

B、阀不严密

C、活塞环损坏

D、进口温度太高，产生汽化