浮头式换热器的缺点是（）。 A.管束不能抽出 B.结构复杂 C.清洗管间和管内不方便

Speaker A: Excuse me. I'd like to exchange this watch. I just bought it, but look at this.Speaker B: ______

A．Yes, I know your watch is new, but I like my old one better.

B．What seems to be the problem

C．Thank you for your kindness, but my watch still works.

D．Sorry. Why didn't you examine it carefully before you bought it

引起肺炎的致病菌有（）

A.副溶血性弧菌

B.铜绿假单胞菌

C.军团菌

D.流感嗜血杆菌

E.蜡样芽孢杆菌

航天员是如何选拔出的，有哪些指标？

假霜霉属的孢子囊形状为（）。

A、椭圆形

B、棍棒形

C、弯月形

D、球形

机械设备出现故障和管路发生堵塞，必须（）后，方可进行检修。

A.停机

B.断电

C.卸压

D.散热