往复活塞压缩机一次工作循环包括()四个工作过程。
A.气体膨胀、吸气、压缩、排气
B.吸气过程、封闭运输、压缩、排气
C.吸气、压缩、膨胀
D.封闭、压缩、排气
参考答案:A
在HBV标记物中,对人体有保护作用的是()。
A.HBsAg
B.抗-HBs
C.HBeAg
D.抗-HBe
E.抗-HBc
Some people like the smell of the flowers but I can't _______ it. [ ]
A. keep up with
B. catch up with
C. end up with
D. put up with