高一英语选择题 需要理由
题目
高一英语选择题 需要理由
It's said that one kind of time machine _____ by a sceientist ,with which man can travel wherever he would like.
A.had been invented B.has been invented
C.had been dicovered D.has discovered
答案
选B.现在完成时的被动语态:have/has been done
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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