在异步电动机单向启动控制线路中，交流接触器的动合触点接在启动控制辅助电路中，实现运转自保功能。
参考答案：对
Because the shop _____, all the T-shirts are sold at half price.[ ]
A. has closed down
B. closed down
C. is closing down
D. had closed down
人体内最大的消化腺是______，具有______、______和______作用．
