单级单吸离心泵主要由泵体、泵盖、叶轮、泵轴、轴封及密封环等组成。该泵叶轮为单吸闭式叶轮，叶片弯曲方向与()方向相反。

A. 田汉
B. 聂耳
C. 贺绿汀
D. 冼星海

A．the thick and long root of the canine.
B．the furcated root
C．the part of the root before furcation
D．the part of the root after furcation
E．the root whose cross section is rounded