单项选择题
A.80%B.85%C.90%D.95%
A.一次方B.二次方C.三次方D.五次方
A.2s,5%;15s,25r/minB.2s,5%;15s,20r/minC.5s,5%;15s,25r/minD.5s,5%;15s,20r/min