对于单级泵平衡轴向推动力的措施有().
A.双吸式叶轮
B.平衡管
C.平衡叶片
D.平衡孔
参考答案:A, B, C, D
There _____ be any difficulty about passing the road test since you have practiced a lot in the driving school. [ ]
A. mustn't
B. shan't
C. shouldn't
D. needn't
关于脑脊液正确的是()
A.自外侧孔流入第三脑室
B.正中孔是脑脊液自脑室入蛛网膜下隙的惟一途径
C.为无色透明不含有机物的液体
D.由脑室脉络丛产生
E.以上均不是