题目

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项.选项中有两项为多余选项. All living things in the ocean are endangered byhumans polluting the water. One way is the dumping(倾倒) of certain waste materials, such as garbage and used water, intothe ocean. The harmful bacteria that feed on the garbage use up much of the oxygenin the surrounding water, so other creatures in the area often don't get enough. Other substances(物质), such as radioactive waste material, can also cause pollution. But after years of being exposed to the ocean water, the自驾游从A地到B地有甲乙两条线路，甲线路是A-C-D-B，乙线路是A-E-F-G-H-B，其中CD段，EF段，GH段都是易堵车路段．假设这三条路段堵车与否相互独立．这三条路段的堵车概率及平均堵车时间如表所示． CD段EF段GH段堵车概率平均堵车时间(单位：小时)2 1  经调查发现，堵车概率在上变化，在上变化．在不堵车的情况下，走甲线路需汽油费500元，走乙线路需汽油费545元．而每堵车1小时，需多花汽油费20元．路政局为了估计段平均堵车时间，调查了100名走甲线路的司机，得到下表数据．堵车时间（单位：小时）频数[0,1]8(1, 2]6(2, 3]38(3, 4]24(4, 5]24 （1）求段平均堵车时间的值；（2）若只考虑所花汽油费的期望值大小，为了节约，求选择走甲线路的概率．