The fact that fun is not equal to happiness may be the opposite of ______ many people actually understand.

---It cost me 30 yuan to get here.
---Well, it was crazy of you to take a taxi        you would come by bus as well.

Children’s brains can’t develop properly_______ they lack protein(蛋白质).

What I want to know is ______ he likes the gift given by us.

Find ways to praise your children often , _____ you’ll find they will open their hearts to you.

______ volleyball is her main focus, she’s also great at basketball.
A  Since   B. Once     C. Unless     D. While

It sounds like something is wrong with the car’s engine. _____ , we’d  better take it to the garage immediately.

Leave your key with your neighbor      _you lock yourself out one day.

Edison was a clever boy, and ______ he was fourteen, he had learned advance mathematics by himself.

You shouldn’t go out without a coat ,         it’s rather cold .