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【判断题】
PLC内有几百个定时器，其功能相当于继电控制系统中的时间继电器。是根据时钟脉冲的累积计时的。时钟脉冲有1ms、10ms、100ms三种，当所计时间到达设定值时，其输出触点动作。A.
正确
B.
错误
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皮皮学刷刷变学霸
举一反三
【单选题】The relaxation of skeletal muscle relies on the activity of the ________, which decreases cytoplasmic calcium concentration.
A.
ryanodine receptor
B.
dihydropyridine (DHP) receptor (L-type calcium channel)
C.
acetylcholine receptor
D.
Ca2+ ATPase
【简答题】下列不属于Word窗口组成部分的是( )
【简答题】Besides calcium and iron, athletes also need______which will help them access energy and pr them from getting ill.
【单选题】We may infer that 'iodine, fluoride and calcium' are______.
A.
substances which act positively or negatively on man's health
B.
harmful substances in the water supply
C.
substances which help provide breeding places for pests
D.
substances contributory to good health
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