英语 请问能这么修改吗?The platform would rise up and down alongside a

英语 请问能这么修改吗?
The platform would rise up and down alongside a skyscraper and pick up people trapped in high stories
改为（增加了：who are ）：
The platform would rise up and down alongside a skyscraper and pick up people 【who are】 trapped in high stories
如果可以的这样修改的话，为什么“who”能省略 他可不是定语从句的宾语啊