?观察与发现
(1) 动词不定式作主语
[观察1]
To know oneself is difficult.人贵有自知之明。
To say is one thing and to do is another.说是一回事，做又是另一回事。
[发现1] 不定式具有名词的特征，可在句子中充当主语。
[观察2]
It's rude to turn your back to your teacher and refuse to answer.
背对着老师、拒绝回答问题是不礼貌的。
It seemed a pity to have wasted so much time.
浪费了这么多时间，真是遗憾。
