离心泵的叶轮分成半开式、封闭式和敞开式三种形式。
参考答案：对
----How did you _________ your vacation?
-----It’s ___________. Everything was really interesting.
A．like, boring
B．think of, boring
C．like, wonderful
D．think of, wonderful
溃疡病一般不合并（）。
A.出血
B.幽门梗阻
C.穿孔
D.息肉形成
E.癌变
