封隔器堵水适用于出水层段岩性坚硬()的生产井。
A、无严重出砂
B、严重出砂
C、出泥浆
D、以上都不对
参考答案:A
He prefers ______ at home reading to ______ out shopping on Sundays.
A.to stay, going
B.to stay, go
C.staying, going
D.staying, to go
呃逆的主要发病机制是()
A.胃气郁滞,失于和降,不通则痛
B.肝气犯胃,胃失和降
C.中焦气机不利,脾胃升降失职
D.胃失和降,胃气上逆
E.胃失和降,上逆动膈