雨淋报警阀组的复位装置不能复位原因是（） A.产品存在质量问题 B.水质过脏，有细小

It was now clear that no such weapons were manufactured and none been found .

A．was found

B．were founded

C．has been found

D．have been founded

In my opinion, hard work is as important as, ______ an efficient way in study. [ ]

A. if not as important than

B. if more important than

C. if not more important than

D. if as important as

皮脂腺的分泌受雌性激素和肾上腺皮质激素的控制。（）

简述空气阻尼式时间继电器的延时原理，如何调整其延时时间长短？怎样将通电延时的时间继电器改为断电延时的时间继电器？