the old man has two sons,both of (whom)are lawyers這是主從復(fù)合句,both of (whom)are lawyers是個(gè)非限制性定語(yǔ)從句比較：The old man has two sons.Both of (them)are lawyers這是兩個(gè)獨(dú)立分句,所以括號(hào)里面的用...定語(yǔ)從句中，介詞在關(guān)系代詞之前時(shí)， 指人只能用whom, 指物只能用which. 記?。。?！第二個(gè)我說(shuō)了是兩個(gè)獨(dú)立的句子了， 后面不是定語(yǔ)從句，當(dāng)然不能用關(guān)系代詞whom了。 更不能用who了