Swimmers must be very strong in order to build up speed because of the high resistance(阻力) of the water. Runners, , must struggle against the heavy resistance of the air and ground.
. His hard work paid ____ when he got the result.
. Are you suggesting that I _____ too old for the job?
Seeing your picture, I couldn’t resist _____ the days _____ we spent together.
______ what we have now, we can’t afford so large a house.
He was _________down for several days after he heard the bad news .