高压脱丙烷塔开车时,塔釜加热的投用时间为()。
A.开车前
B.投料时
C.建立回流后
D.进料后塔釜出现液面
参考答案:D
The beautiful girl stood there until the train ___________.
A.lost sight
B.caught sight
C.was out of reach
D.got out of sight