THEY ... ALL YESTERDAY MORNING.A. CLEANING THE FLOORB. WERE CLEANI...

11. - 3500 CAU TRAC NGHIEM ON TAP AV THCS
3500 CAU TRAC NGHIEM ON TAP AV THCS

11. They ... all yesterday morning.

a. cleaning the floor

b. were cleaning the floor

c. was cleaning the floor

d. cleaned the floor

 b