如图所示，物体重10 N，它与竖直墙面的接触面积是0.5 dm²，现用24 N的水平力把物体按在墙上，墙面受到物体的压力和压强分别为 （  ）

下列说法正确的是（　　）

在学习“探究影响电流热效应的因素”时，同学们发现用电阻丝对煤油加热时，观察温度计的示数变化的过程非常耗时，为了减少实验的时间，他们提出了如下改进的设想：

设想一：将煤油换成水来做实验;

设想二：通过加热空气来做实验。

阅读短文，下列问题

 B

American boys and girls love to watch television. Some children spend six hours a day in school and four to six hours a day in front of the television set. Some even watch television for eight hours or more on Saturday.

     Televisions are like books or films. A child can learn bad things and good things from them. Some programmes (节目) help children to understand (理解)the news, others show people and places from other countries or other time in history. With television a child does not have to go to the zoo to see animals to the ocean to see a ship. Boys and girls can see a play, a concert or a game at home.

     Television brings many places and events into our homes. Some programmes show crime (犯罪) and other things that are bad for children, so parents sometimes help them to find other interesting things to do.