Before he became a teacher,he has been a salesman for years 改错

问题描述:

Before he became a teacher,he has been a salesman for years 改错

如果要改错的话,后面应该用had been过去完成时,因为表达的是过去的过去。

在他当老师之前,他做了很多年的推销员

He had been a salesman for years before becoming a teacher.

把后面的has been 改成 had been