题干

如图,一带负电粒子以某速度进入水平方向的匀强电场中,仅在电场力作用下形成图中所示的运动轨迹。M和N是轨迹上的两点,其中M点在轨迹的最右点。下列表述正确的是学(    )

A:粒子做匀变速曲线运动

B:粒子受电场力方向向右

C:匀强电场方向向左

D:粒子在M点的速率最大,电势能最小

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A

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    City people usually think they are a lot smarter than country people. They often laugh at simple country ways. But people do not laugh at country music. It is one of the most popular kinds of music in the United States today.

    Perhaps it is so popular because it is about simple but strong human feelings and events—love, sadness, good times and bad times, it tells real life stories and sounds the way people really talk. As life becomes more and more complicated(复杂的), it is good to hear music about ordinary people.

    Country music, sometimes called country western, comes from two kinds of music. One is the traditional music of the people in the Appalachian Mountains in the eastern United States. The other is traditional cowboy music from the West. The singers usually play the guitars, and in the 1920s they started using electric guitars.

    At first city people said country music was low-class. It was popular mostly in the South. But during World War Ⅱ, thousands of Southerners went to the Northeast and Midwest to work in the factories. They took their music with them. Soldiers from the rest of the country went to army camps in the South. They learned to like country music. Slowly it became popular all over the country.

    Today country music is popular everywhere in the United States and Canada, in small towns and in New York City, among black and white, and among educated and uneducated people. About 1,200 radio stations broadcast country music twenty-four hours a day. People sing it in their languages. The music that started with cowboys and poor farmers is now popular all over the world.