I have been an engineer for more than ten years,but I was once a worker for three years.
题目
I have been an engineer for more than ten years,but I was once a worker for three years.
这里was once a worker 为什么不是had been a worker?
答案
因为主句用了过去完成时,从句用一般过去时表示曾经做过某一*******
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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