正常情况下，起钻前要循环钻井液（）。
A、一周
B、一至两周
C、三周
D、三至五周
参考答案：B
—What are we going to do on Sunday?
—How about ______? [ ]
A. going bike riding
B. to go bike to ride
C. going to bike riding
D. to go bike riding
一般矿床开采的全矿井负压应小于等于（）pa。
