Nancy spent half an hour _______ playing the piano every day.
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.
—_____ you _____ your homework yet? —Yes, I _____ it ten minutes ago.