(last week) (a old friend of mine) (came to) beijing and (paid me a visit)四个括号里的,哪个错了呢?应该怎么改?

问题描述:

(last week) (a old friend of mine) (came to) beijing and (paid me a visit)
四个括号里的,哪个错了呢?应该怎么改?

第二个括号里的a改成an