对于油层薄、跨度大、层数多的油井，通常采用（）压裂方式。
A.投球
B.卡封
C.合压
D.限流
参考答案：D
—Mike got “F” in his history test．
一 ? He has been working so hard on it．
A．How come
B．So what
C．What for
D．Why not
注释法学派
