there are people (whose) only on-line activity is emailing 为什么用那个
问题描述：
there are people (whose) only on-line activity is emailing 为什么用那个
答
who's 表示谁是
whose表示谁的.
你就记住:
隐含的回答是某个人的,这里是那群人（people）的表示所有格,你就填whose,不管是他的,她的,还是你的,你通通填whose.
如果隐含的回答是某个人,那就用who's.