氩气瓶工作压力为( )MPa。
A.15
B.18
C.20
D.22
参考答案:A
---Has your father come back from Africa?
--- Yes, but he ______ here for only three days before his company sent him to Japan.
A.was
B.has been
C.will be
D.would be
污水处理站的二氧化氯发生器药剂投加部分通常设两台计量罐,含磁翻板液位计,通过()进行准确计量。
A.计量泵
B.涡轮流量计
C.电磁流量计
D.水表