1.有些动词或短语后面只能跟动词的-ing形式作宾语，而不能用不定式： eg.：admit, avoid, consider, enjoy, finish, mind, suggest, practice, give up, look forward to, be used to, put off… eg.：i am considering (give) him some advice, we are used to (live) here. 2.动词-ing形式的否定式为: not + ving eg.：they regret not helping the boy. 3.有些词后面既可以跟-ing，又可以跟to do，但意义有所差别。 remember to do sth. remember doing sth. forget to do sth. forget doing sth.
