—Paper ___________ wood. We should not waste paper.—I agree. I always use __________ sides of paper.
Put it down,Tom. You mustn’t read______letter.
They often had fun ______ ball games before. But now they have no time ______ after-school activities.
—Don’t play with fire. —_________.
Daniel had one month_____last summer and he took a course _____DIY.
We can put the prefix “un-” before the following words to give them the opposite meaning except(除了)_____ .