阅读下列短文，从每题所给的四个选项A、B、C和D中，选出最佳选项。
A
Members of the working class have blue-collar jobs. They are construction workers, truck drivers, mechanics, steel workers, electricians, and the like. What makes this class differ from the lower class is, first, longer periods of employment -- and therefore, more fixed incomes —and, second, employment in skilled or semiskilled (半熟练的 ) occupations, not unskilled ones. Although unemployment hits all levels of the American economy, including those of skilled and semi-skilled workers, it is most common at the bottom of the class structure and increasingly less common at each level upward. They consider themselves to be respectable and hard working and they look down upon members of the "lower" class, whom they often consider to be lazy, dishonest, and too ready to exploit
