用所给单词的适当形式填空.

1. _____ (do) she live on Center Street?

2. The food market is _____ (open) for 24 hours.

3. It's very far. You can _____ (take) a taxi.

4. Our teacher often _____ (arrive) at school early in the morning.

5. The boy _____ (clean) his classroom every morning.

串的长度是

A．串中不同字符的个数

B．串中不同字母的个数

C．串中所含字符的个数且字符个数大于零

D．串中所含字符的个数