Mr.Smith is the only one of those foreigners (who) is working in China.这句话中为什么是用who来作为关系代词呢?the only不是已经出现了吗?只能用that?还是说the only修饰的是one,不是先行词foreigners,所以才用who,那若是这样,that不也就可以替换拉么?请大家帮帮忙,解决一下!谢谢了!!!