only先行詞|the

先行詞有the only，the very，the just修飾時，只用that.

He is the very man that helped the girl out of the water .，3，如果先行詞是表示人的不定代詞時，只能用who，否則都可以。用the only修飾物時，只能用that不能用which引導定語從句。，2，that

只能用that的情況

序數詞、最高級、the very+名詞、the only+名詞、all之後等等，0，應該用that，0

the only做先行詞時，後面關係代詞用that.

例句：This is the only book that is worth reading.