She won’t lose weight______ she keeps a diet and takes exercise every day.

—Oh! I failed again.
—Don’t lose heart. One more effort (努力), _________ you will succeed.

_____ it was very cold, _____ my friend still went swimming   in Jialing River this morning.             

The math problem is so hard. I really don’t know     .

—Mary，I don’t know ____ you can come tomorrow morning.
—No problem! I’ll be here _____I’m free then.

—Little Kate went to the concert_______it rained heavily yesterday.

—Tom isn’t feeling very well.  
—He seems to have a cold      the weather changes suddenly.

We’ll go to the Summer Palace _____it doesn’t rain this Saturday.
A. when            B. if              C. until

Sam isn’t leaving________next Sunday.
A. When           B. until             C. after

You should get up early _______ you would catch the train.