探究发现
①Learning without thinking leads to confusion; thinking without learning ends in danger.
②Being exposed to sunlight for too much time will do harm to one's skin.
③I'm sorry for having kept you waiting so long.
④Seeing that she was going off to sleep, I asked if she'd like that little doll on her bed.
⑤Some teachers might be angry for not having been informed in advance.
[我的发现]
1．动词ing形式由“do＋ing”构成。
2．动词ing形式的否定形式直接在前面加not。
3．动词ing形式有一般式、完成式、一般被动式和完成被动式四种。
