The practice of hanging clothes across the street is a common ___ in many parts of the city.

A．look

B．sign

C．sight

D．appearance

叶片泵是利用安装在泵轴上的叶轮高速旋转，叶片与被输送液体发生力的相互作用，使液体减少能量，以达到输送液体的目的。