钻井时,应注意保证()清洁,防止因杂质混入造成丝扣部分异常磨损。
A、泥浆
B、钻杆表面
C、动力头
D、上下接头丝扣
参考答案:D
I shall never forget those years_____ I spent in the factory with the workers, _____has a great effect on my life.
A.when, that
B.that, which
C.that, that
D.when, which
剑突下区声窗不能检查哪个切面()。
A.四腔心切面
B.肺动脉长轴切面
C.左室短轴切面
D.双心房切面
E.主动脉弓短轴切面