before引导的从句为什么不用一般现在时代替将来时

问题描述

It won't be long before his boy will help the girls with their bags.

老师答疑

刘老师：

It won't be long before his boy will help the girls with their bags.

【翻译】用不了多久，他儿子就会愿意帮那些女孩子拿行李袋了。

【答】在时间、条件、让步等状语从句中，即便两个动作都是将来发生，语法也不允许主从句都用将来时。规定从句使用一般时才代替将来时。

在before his boy will help the girls with their bags 这个时间从句中，will help意思是“愿意帮助”。will是情态动词，表示人的意愿、愿望；不表示将来。又如：

If you'll excuse me for a while, I'll find out for you.  请稍候片刻，我给您查一下。（您若愿意等的话）

If you will keep waiting for a while, I'll help with your enquiry. 请你再等一会儿，我要帮您解答一下。