A.0 B.-1 C.1 D.-1或1A.0 B.-1 C.1 D.-1或1

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问题

选项 A.0
B.-1
C.1
D.-1或1

答案B

解析根据题意,有a2=1,解得a=1或-1.根据集合的互异性,排除a=1,从而a=-1.
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