go and ask the assistant how much does the coat costs

题目

go and ask the assistant how much does the coat costs
为什么不用does啊

答案

1. how much the coat costs在句中做ask的宾语从句,即ask sb sth中的sth；
而宾语从句的句序为“引导词how much + 陈述句”,所以写成the coat costs这样的主谓陈述句序.
再如：I want to know how old you are.
2. 如果加does,一则后面的costs要还原成动词原形cost,二则它只能做一个单独的疑问句,即：How much does the coat cost?
它不能在复合句中充当从句.
3. does the coat cost是所谓的疑问句序,或者语法书上所谓的倒装句序.