雾与霾的主要区别包括：雾的水平能见度小于1公里，霾的水平能见度小于10公里。雾的相对湿度大于90%；霾的相对湿度小于80%，相对湿度介于80～90%是霾和雾的混合物，但其主要成分是霾。雾的厚度只有几十米至200米左右，霾的厚度可达1－3公里左右。雾的边界很清晰，过了“雾区”可能就是晴空万里，但是霾与晴空区之间没有明显的边界。雾的颜色是乳白色、青白色，霾则是黄色、橙灰色。雾一般午夜至清晨最易出现；霾的日变化特征不明显，当气团没有大的变化，空气团较稳定时，持续出现时间较长。

    Have you read the book called Uncle Tom's Cabin? It's said that it is one of the greatest books in America．The book ____an unpleasant social problem—slavery(奴隶制)in the Southern States of America. It first came out in 1852．Over 300,000____were sold out in a year．People had ____ideas about the book．In the North, more and more people began to____theft support(支持)for the freedom(自由)for the black people after they read the book, but in the South, many people were very____at the people in the North. In 1861, the war between the two parts of the country____. Uncle Tom's Cabin surely played a part in the ____. In 1862, Abraham Lincoln met Harriet Beecher Stowe, the book's ____. As he took her hand. Lincoln said, "So this is the little lady who started this big war."