滚装客船货物出入口门路应是具有()的结构。
A、足够强度
B、水密性
C、A+B
参考答案:C
35. It was the fifth time that he ______ to such a meeting.
A.have been invited
B.was invited
C.had invited
D.had been invited
通常所说的一次汽化也称为()蒸馏。