在CNG加气站加气，当加气压力达到（）时，应停止加气。
A.10MPa
B.15MPa
C.20MPa
D.25MPa
参考答案：C
单项选择。
— —Yes, it is.[ ]
A. Is this your aunt?
B. Is this your pen?
Great changes have taken place in that factory. It is no longer _________
it was 20 years ago,_____ it was so poorly equipped.
A．what ,when
B．that ,which
C．what ,which
D．which ,that
