Today's nuclear fission fuels are the remnants of which(A)used to be a much more(B) active mixture of radioactive and fissionable materials two billion years ago(C) and earlier(D)
为什么选A啊？作者: ★vivien★ 时间: 2004-4-16 20:03
of which错了，remnants是which的先行词，后面从句里并没有和of搭配的动词
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