下列五个命题:       ①满足z·=1的复数只有±1、±i;      

下列五个命题:

       ①满足z·=1的复数只有±1、±i;

       ②若z∈C

,则z2≥0;

       ③若z∈C

,则|z|2=z2;

       ④互为共轭的两个复数之差为纯虚数;

       ⑤复数z=a+bi(a、b∈R

),当a=0时,复数z对应的点在虚轴上.

       其中正确命题的个数为(  )

    A.0      B.1  C.2      D.3

      

答案

B

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