Question

Error Identification

Before he retired last month, Mr. Smith has been working as  a secretary  in the House of Parliament.

Answer 1

-Thì quá khứ hoàn thành diễn tả 1 hành động xảy ra trước 1 hành động trong quá khứ

-Công thức: Before + S + Ved/ V2, S + Ved/ V3

has been working => had been working

=>Before he retired last month, Mr. Smith had been working as  a secretary in the House of Parliament.