If you live in Changchun, you may notice that the air in winter is not as _______as it is during the summer.
A.clean B.cleaner C.cleanest D.cleaning
—I forgot to bring my notebook here. Could you please lend me two________, Linda?
—OK, here you are.
A.paper B.papers C.piece of paper D.pieces of paper
Knowledge can make________ difference in our life and change the world.
A.a B.an C.the D./
The Chinese language has become a ________ to connect China with the other countries.
Astronauts sometimes feel ________ in space because they can't see other people there.
Children dress up and visit the houses in their neighborhood asking ________ sweets.
