they are the visitors-------- come from america.a what b that c whom d which 怎么选

问题描述:

they are the visitors-------- come from america.a what b that c whom d which 怎么选

B
定语从句-------- come from america当中缺少指代“人”的主语
A不用于定语从句
C只能作宾语
D不指代人
只有B,既能做主语,又能指代人.