The experts from the zoo were convinced that the animal was a puma,but where had it come from
题目
The experts from the zoo were convinced that the animal was a puma,but where had it come from
为什么不用where did it come from
答案
had come是过去完成时,表示过去的过去发生的动作.原句中were convinced动作发生在come之后.
举一反三
已知函数f(x)=x,g(x)=alnx,a∈R.若曲线y=f(x)与曲线y=g(x)相交,且在交点处有相同的切线,求a的值和该切线方程.
我想写一篇关于奥巴马的演讲的文章,写哪一篇好呢?为什么好
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