单选题 A survey revealed that on average, college students spend almost as much time on ______ mobile phones as they spend doing physical activity.
【正确答案】 B
【答案解析】[解析] 语法：代词
1．选项均为代词。
2．名词mobile phones前应使用代词所有格，代词所有格可与形容词一样，修饰名词。