同一层煤在相同浓度情况下，走向方向的任何地点瓦斯含量和瓦斯涌出量都相同.
参考答案：错
发生在球部的溃疡约占十二指肠溃疡的（）
A.50%
B.60%
C.70%
D.80%
E.90%
— When is he willing to lend his friends some money?
— Only when ______ hard enough.
A．to press
B．pressed
C．pressing
D．is pressed
