回顾20世纪上半叶，美国经历了经济危机，二战，珍珠港事件。而在50年代，艾森豪威尔就任总统，美国经济开始稳定，青少年数量增长，中产阶级也逐渐增多。
20世纪50年代，美国流行音乐市场主要有两种音乐，BLUES和乡村音乐。大量的翻唱歌曲出现，很多人就厌倦了这些音乐。这时，摇滚诞生了。
麻烦不要贴在线翻译的网址，帮忙翻一下，谢谢
參考答案:Reviewed the first half of the 20th century, U.S.A. went through the economic crisis, World War II, Pearl Harbor Incident. In the 1950s, Eisehower took up the post of the president, U.S.A.'s economy began to be steady, teenagers' quantity increases, the middle class increases gradually too.
In the fifties of the 20th century, mainly there are two kinds of music, BLUES and country music on the market of American pop. Looking through the song of singing to present of a large number of, a lot of people are tired of the music. At this moment, the rock was born.
翻译仅供参考