下列物质的沸点最高的是 （）

    Many children like watching TV．It's very interesting and they can see a lot and know many things about other people．They can also learn from the radio．But they can learn easily with TV．Why? Because they can hear and watch at the same time．But they can't watch anything from the radio(收音机)．TV helps to open children's mind(思想)．They can find better ways to do things．

    Many children watch TV only on Saturday and Sunday nights．They are busy from Monday to Friday．But some children watch TV every night．They go to bed very late．It's not good for their eyes and health.

质量均为m的两物块A和B之间连接着一个轻质弹簧，其劲度系数为k，现将物块A、B放在水平地面上一斜面的等高处，如图所示，弹簧处于压缩状态，且物体与斜面均能保持静止，已知斜面的倾角为θ，两物块和斜面间的动摩擦因数均为μ，设最大静摩擦力等于滑动摩擦力，则下列说法正确的是（   ）

如图为“北京市气温曲线和降水柱状图”，据图说出发展农业的有利条件是（　　）