滑轮按使用方法分为（）。
A、导向滑轮
B、动滑轮
C、定滑轮
D、定滑轮、动滑轮、导向滑轮
参考答案：A
Some social workers _____ after the people in need while others ____ out food to the local people.
A．looked, gave
B．were looking, gave
C．were looking, were giving
D．looked, were giving
自动变速箱变扭器内锁止离合器的作用是（）
A.使运转平顺
B.防止发动机熄火
C.增加扭矩
D.降低油耗
