多级离心泵轴向力主要用（）方法来平衡。
A.叶轮上开孔
B.平衡管
C.平衡叶片
D.平衡盘
参考答案：D
I've decided to keep all these stamps as they might be ________ some day.(2012·天
津联考)
A．of great value
B．much valuable
C．of many value
D．very valuable
地仓（Dìcāng，ST4）足阳明胃经
