從句中如果是介賓的話,介詞與先行詞放在從句前,這時(shí)引導(dǎo)詞不可省略,而且引導(dǎo)詞只能用which,不能用that.
先行詞是形容詞的最高級(jí),序數(shù)詞,only.last 或者very,這時(shí)候只能用that.
當(dāng)先行詞本身是不定代詞：anything,nothing,all,little,much,這時(shí)只能用that 來(lái)引導(dǎo).
先行詞是一個(gè)既有人又有物的詞組時(shí),這時(shí)候只能用that 來(lái)引導(dǎo).
當(dāng)主句的疑問(wèn)詞時(shí)Who時(shí),定于從句只能用that來(lái)引導(dǎo).
比如：Who's the man that is smoking over there.