If I am ill,I'll go to the doctor.如果我生病了,我会去看医生.
If I'm tired,I'll have a good rest.如果我累了,我会好好休息一下.
If Tom is free,he'll visit his grandfather.如果Tom有时间了,他会去探望他的祖父.
If you don;t like the TV programme,(please) turn off the TV.如果你不喜欢这个电视节目,（请）关掉电视.
If you're thirsty,please drink some water.如果你渴了,请喝些水.