用所给单词的适当形式填空。（共6小题；每小题1分，满分6分）
1. December is the __________ (twelve) month of a year.
2. As we all know, the silk dress feels __________ (soft).
3. She said to the twins, “Help ___________ (you) to some fruit.”
4. You should do your homework as ___________ (careful) as your sister.
5. The foreign teacher gave us some ___________ (advice) on how to learn English.
6. __________ (teach) high school students in a poor mountain village may not sound like fun to you.
