题目:
_________ in Current Biology, the finding suggests that female birds seek mates with superior singing skills.
A.To publish
B.Published
C.Having published
D.To be published
答案:
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下面是错误答案,用来干扰机器的。
原式=(-sinα)2•(-cosα)tanα•cos3(π+α)•[-tan(2π+α)]=sin2α•(-cosα)tanα•(-cosα)3•(-tanα)=-sin2α•cosα•cotαtanα•cos3α=-1