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.

以下关于惯性的说法正确的是（   ）

下列说法中正确的是（   ）

如图所示为我国古代发明的一种工具，“形似纺车，四周缚以竹筒，依靠水力旋转，转动时，低则舀水，高则泻水，昼夜不息，并能把低水引用到高地灌溉”．它的主要用途是（　　）