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【单选题】
Which of the following is not tree?A.
When a person tries to help others, he must be clear that there is a real emergency.
B.
When a person tries to help others, he should know whether they are worth his help.
C.
A person must take the full responsibility for the safety of those in emergencies if he wants to help.
D.
A person with a heart attack needs the most.
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举一反三
【单选题】相间短路时瞬时电流速断保护不能保护本线路全长，这是因为（ ）。
A.
为了保证电流速断保护有足够的灵敏度
B.
为了保证电流速断保护的选择性
C.
为了保证电流速断保护的速动性
D.
保护装置的固有缺陷，无法将定值调整到线路全长的整定值