GB151中要求：对接后的换热管应逐根进行液压试验，试验压力为设计压力的1.5倍。
参考答案：错
—Are there any boats in the river?
—No, _____.[ ]
A. there isn't
B. there are
C. there is
D. there aren't
中枢神经兴奋药按其主要作用部位和效应分哪几类？
