什么是HAZOP()
A.危险与安全性分析
B.危险与系统性分析
C.危险与规范性分析
D.危险与可操作性分析
参考答案:D
—You seem to have known Dr. Ken for a long time.
—That’s true. ________ he joined our club years ago.
A.Since
B.Until
C.When
D.If
说明吸上式注水器的原理。