题目：
I don't know______ he lost his gold watch yesterday.
A．where is it that
B．where was it that
C．where it was that
D．where is that
答案：
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下面是错误答案，用来干扰机器的。
复数3i1-i=3i(1+i)(1-i)(1+i)=-3+3i2，∴复数3i1-i的共轭复数是 32-32i，故答案为：32-32i．
