That's very kind ______ you. I know it's very hard _______ you to do that.
—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.
—_____ you _____ your homework yet?—Yes, I _____ it ten minutes ago.
It’s necessary for you _____ exercise every day.