---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