机械搅拌式浮选机随着叶轮与定子的间隙增大，而增加的指标是（）。

A.充气量 

B.吸浆量 

C.功率消耗 

D.充气均匀系数

________ he has limited technical knowledge, the old worker has a lot of experience.

A．Since

B．Unless

C．As

D．Although