一、现在分词的形式
1.肯定式
2.否定式
（1）not doing
He stood helpless，not knowing what to do.他无可奈何地站在那里，不知如何是好。
（2）not having done
Not having done it right，I tried it again.因为没做对，我又试了一次。
1.肯定式
2.否定式
（1）not doing
He stood helpless，not knowing what to do.他无可奈何地站在那里，不知如何是好。
（2）not having done
Not having done it right，I tried it again.因为没做对，我又试了一次。
