--- I have trouble _______ my new computer.---Don’t worry. I’ll show you how _______it.A. using; using B. to use; to use C. using; to use
_____ the environment is important for human beings.
I can’t stand _____ for you so long.
—Is the bag beautiful? —Yes, at _____ it’s _____ the one you bought for me.
Our teacher told us that light _____ much faster than sound.
In our class _____ of the students _____boys.