教学目标：
1. understand the function and part of speech of verb-ing.
2. know that such words as admit, dislike can only be followed by verb-ing form, not an infinitive.
3. know that such words as continue, prefer can be followed by verb-ing form or an infinitive with little difference in meaning.
4. know that such words as forget, regret can be followed by a verb-ing form or a to-infinitive, but with some difference in meaning or usage.
5. fill in the blank with a correct form of verb.
