矿井瓦斯涌出量与工作面回采速度成正比。
参考答案:对
Tom as well as two of his friends ______ to the concert last night.
A.has been invited
B.had been invited
C.were invited
D.was invited
气剂201用于焊接()。
A、不锈钢
B、铸铁
C、铝合金
D、铜合金