i don't think it will be of use （reason with ）him.为什么括号里用这个?

(reason with)表示用这个词组的适当形式填空
可以填I don't think it will be of use reasoning with him.
It is not use doing sth.是种固定搭配,后面要用动名词,表示……没用.这里I don't think 是把not提前了,这也是固定用法,不是表示我不认为,而是表示我认为……不……
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