单作用叶片泵的叶片倾角应顺着转子的回转方向（）。
A.前倾
B.后倾
C.前倾后倾皆可
D.成法线方向布置
参考答案：B
禁止参与竞买规则中，禁止委托人参与竞买即禁止委托人参与自己委托拍卖标的的竞买。（）
To ____ this happening again, John commanded that the source of all the water supplies ___ . [ ]
A. stop, was examined
B. keep, should be examined
C. prevent, examined
D. stop, be examined
