A.1.3 B.1.5 C.1.7 D.2
A.80% B.75% C.85% D.90%
A.4 B.5 C.6 D.7
A.4 B.10 C.15 D.20
A.切断电源 B.使电动机停止转动 C.用软管拖拉 D.随时