Each girl present at the party was wearing a flower in the hair, which__________their beauty.

A．added

B．added up

C．added to

D．added up to

摩擦对机械运动部件的不良作用有（）。

A.消耗大量的功和能

B.机械部件的磨损

C.产生热量

D.减少阻力