泵壳的作用是将叶轮甩出来的高速（）经蜗形流道减速后汇集起来变为压力能，导向泵的出口。
A、液体
B、气体
C、转速
D、固体
参考答案：A
两个锐角的和一定是钝角．______．
Since then, the suspect has been under close watch of New York’s police.
A. under close survelliance B. under immediate supervisionC. at the inspection D. at the mornitoring
