Each country has many kind people who volunteer to take care of others.  For example, some high school and university students, in the US often spend many hours as volunteers in the hospitals or old people's homes. They read books for the people or they just visit them and play games with them or listen to their problems.

    Other young volunteers go and work in the homes of the sick people. They clean up their houses or do the shopping. For boys who don't have fathers there is an organization called "Big Brothers". University students and other people take these boys to play baseball games and help them get to know the things that boys usually learn from their fathers.

    Each city has a lot of clubs where boys and girls can go to play games or take part in other activities. Some of these clubs show movies or have short trips to the mountains, the beaches or the museums. Most of these clubs use a lot of high school and university students as volunteers, because they can understand the problems of these boys and girls more easily.

    Volunteers believe that some of the happiest people in the world are those who help to bring happiness to others.

猜想1：点燃火柴的快慢与凸透镜的焦距大小有关；

猜想2：点燃火柴的快慢与凸透镜的直径大小有关。

图中的汽车是我们熟悉的交通工具，它给我们的生活提供了便利．汽车应用了许多物理知识，完成下面各小题：

关于“周末做学科作业时间”这组数据说法正确的是（       ）