液空液面正常，主冷液面下降，为保证制氧机正常运行，应该（）。
A.开大液空节流阀
B.增加膨胀量
C.减少氧产量
D.减少氮产量
参考答案：B
It is said that people are________ likely to tell lies over the phone as they are in emails.
A．as twice
B．twice as
C．twice more
D．twice than
我国第一个海上油田在（）海域。
A、东海
B、南海
C、黄海
D、渤海
