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(图表) 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.

已知某几何体的三视图（如图），其中俯视图和侧（左）视图都是腰长为4的等腰直角三角形，正（主）视图为直角梯形，则此几何体的体积V的大小为（   ）

解决水资源空间分布不均问题的主要途径是（　　）