Tom’s desk is always clean and tidy. —Yes, he hisschool things every day.

________ mooncake on the plate looks delicious.I want to eat ________．

Not until all the fish died in the river ____ how serious the pollution was. [ ]

Has Mary ever visited Tower Bridge—Yes. She ______ it two years ago.

21．All parents are willing to risk ________ their lives tosave ________ of their children when a disaster is approaching.