I am used to traveling by air and only on one occasion have I ever felt frightened.

问题描述:

I am used to traveling by air and only on one occasion have I ever felt frightened.
have I 在句中为什么这么用为什么要加have,

have 是助动词 这个句子是用only 把状语提前 后面就要用倒装语序 再说后面的是完成时 所以就把助动词only 提前拉