---Why is the classroom so dirty? --- Sorry, sir. It ______ yesterday. We forgot to do it. 
#44831
A
doesn’t clean
B
didn’t clean
C
isn’t cleaned
D
wasn’t cleaned
推荐题目
 —Smoking _________in the cinema. Please stop _________. —Sorry, I won’t.
#44571
A
is allowed; smoking
B
allows; to smoke
C
isn’t allowed; smoking
D
isn’t allowed; to smoke
 Personal computers ______ in 1976. It has changed the whole world.
#44711
A
have invented
B
were invented
C
is invented
D
invented
— Dad, may I go out with my friends? — Unless your homework          .
#44465
A
has been finished
B
has finished
C
finishes
D
will finish