真空沸腾式海水淡化装置正常使用中最容易漏气而使真空度降低的地方通常是()。
A.蒸馏器盖板
B.蒸馏器真空破坏阀
C.凝水泵轴封和阀杆填料
D.海水泵轴封和阀杆填料
参考答案:C
People ______ running everywhere. Do you know what_______? [ ]
A. see; has happened
B. are seen; is happening
C. be seen; has happened
D. see; happens
简要说明快中子在物质中含H物质中的慢化吸收过程。