测试限位开关的有效性要在电梯空载检修状态下，向上（下）点动运行电梯，直到轿厢不能运行为止，此时电梯应能反向运行（）
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新队章增加了入队誓词的条款，具体内容是：我是中国少年先锋队队员。我在队旗下宣誓：我热爱中国共产党，热爱祖国，热爱人民，好好学习，准备着：为共产主义事业贡献力量！
A. 正确
B. 错误
幻灯片在放映过程中终止放映的按（）键。
A. Ctrl
B. Alt
C. Del
D. ESC
Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?（）
A. The pump delivers full capacity when started, but gradually slackens off toan abnormally low flow
B. The pump packing gland overheats after short operating periods
C. The motor over-current protective device continually shuts the pump down
D. Pounding noises can be heard at the pump suction chest
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