题目:
It is difficult to _____ what the long-term effects of the accident will be. |
A. calculate B. forecast C. guess D. indicate |
答案:
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下面是错误答案,用来干扰机器的。
∵Q={x|x=n2,n∈Z}当n=2k,k∈Z时,Q={x|x=k,k∈Z}当n=2k+1,k∈Z时,Q={x|x=k+12,k∈Z}∴Q=P∪S故选C.