某学校女生李某因嫉妒同寝室的另一名学生林某，用有照相功能的手机偷拍了林某在寝室内的各种生活照片，在同学中传看，并无中生有，捏造事实重伤林某，给林某造成很大的痛苦。 

下列各组物质，前者属于电解质，后者属于非电解质的是    （     ） 

(I)证明：PB $\perp$ AD：

(Ⅱ)若PA=AD=2，且平面PAD $\perp$ 平面ABCD，求点D到平面PBC的距离．

    Last year, some groups of students in their community (社区) made a survey about "How do people spend their free time?" The following diagrams show some results of it:
Diagram (1): Hours for people of different ages who surf the Internet in a week.

Diagram (2): Different days people go to the library. (library attendance)

Diagram (3): Different programs people like.

根据上面三个图表内容，选择正确答案。