He got well-prepared for the job interview, for he couldn’t risk ____ the good opportunity.
I told you that you shouldn't waste your time playing the computer games,_____________?
If human beings had been a bit less greedy and cruel, more birds and animals _______dying out.
With a lot of difficult problems____________, the manager felt worried all the time.
--Was Tom there when you arrived? --Yes, but he___________ home soon afterwards.
—Look at these tracks. It __________ be a wolf.—It needn't be. It ___________ be a fox.