题目内容：

sister asked me to go there by train,because the train ticket is ()the plane ticket
A as cheap three times as.B as three times cheap as.C three times cheaper than.D cheaper three times than

优质解答

C,希望帮到你

追问：

能解释下为什么吗- -？

追答：

几倍就是用这种表达法，你记住就行