HE IS WORKING IN THAT FIRM. HE ... THERE SINCE 1978.A. HAD WORKEDB...

17. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

17. He is working in that firm. He ... there since 1978.

a. had worked

b. has been working

c. was working

d. will be working

 b