Sometimes, gerund or infinitive can also used to be the subject of the sentence.

動名詞和不定詞也可以當作句子的主詞.

For example: (a) Riding with a drunk driver is dangerous.

           (b) To ride with a drunk driver is dangerous.

當例句(a)以 Gerund 動名詞當主詞時,例句(b)以不定詞當主詞.兩句所傳達的意思一樣.

* 例句(b)也可以改寫為以It開頭的句子:

              It is dangerous to ride with a drunk driver.