各类业务资料的保管期限,自保险合同终止之日起计算,不得少于( )

W：Why are you just standing outside instead of going in？M：I have tried all my keys in the lock，but it won’t open.Q：Why didn’t the man go in？（）

A．The door needs repairing.
B．He bad lost all his keys.
C．He couldn't open the door.
D．He wanted the woman to help him.

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已知m，n是实数，且当x>2015时，mx－2＋nx＋2=5x＋2x2－4恒成立，则m2－n2=（）. 点击查看答案