压井效果好坏取决于压井液压力与油层压力的对比关系和（）。
A.压井本身的性质
B.井深
C.PH值
D.胶体率
参考答案：B
这个标志是何含义？（）
A．堤坝路
B．上陡坡
C．连续上坡
D．下陡坡
— Catherine, I've cleaned the room for you.
— Thank you. You _____ it. I could manage it myself. [ ]
A. needn't do
B. needn't have done
C. mustn't do
D. shouldn't have done
