WHEN HE ..., I ... MY HOMEWORK.A. CAME / WAS DOINGB. HAS COME / DO...

20. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

20. When he ..., I ... my homework.

a. came / was doing

b. has come / do

c. was coming / have done

d. comes / was doing

 a