根据句意及首字母提示完成句子。

1. —Did your sister use to have straight hair?

    —No, she used to have c_________ hair.

2. Mr. Green is really s _________, for he never smiles.

3. Amy used to be quiet, but now she is very o_________.

4. —Did you u ________ to play the piano?

    —Yes. I used to play the guitar, too.