--- Do you know what Tom does all day ?---- I know he spends at least as much time watching TV as he ____________his lessons.
I ________ through that bitter period without your generous help.
By the time Jack returned home from America, his son __________ from college.
She was good at physics _________she found it boring.
The experiment show that proper amount of exercise, if ________ regularly, can improve our health.
Listen! Do you hear someone _________ for help?