I / arrive / 7 am / th^post office / open

  I / arrive / 7 am / th^post office / open

GRAMMAR (Ngữ pháp)

Đề bài:

a.      When I arrived at 7 a.m., the post office which had just been opened.

b.      When I arrived at 7 a.m., the post office had just been opened.

c.      I arrived at 7 a.m. when the post office had just been opened.

d.      I arrived at 7 a.m. at the time the post office had just opened.

b.      When I arrived at 7 a.m., the post office had just been opened.