Although the United States has been shaped by continual waves of immigrants, Americans have often viewed immigration as a problem. Established Americans often look down on new immigrants. Despite such tensions, economic needs have always forced Americans to seek immigrants as laborers and settlers, and economic opportunities have appealed to foreigners. The vast majority of immigrants to the United States have come in search of jobs and the chance to create a better life for themselves and their families.In all of American history, less than 10 percent of immigrants have come for political or religious reasons.Economic immigrants from Europe, Asia, and Latin America have come to the United States voluntarily. Others, most African Americans, were involuntarily transported to North America to do forced labor or to be sold as slaves. Regardless of the reasons they come to the United States, new immigrants typically work in labor-intensive, low-paying, and dangerous jobs--occupations that most other Americans avoid.Although immigrants are expected to absorb the beliefs and standards of the dominant society, most immigrant groups try to maintain their own cultural tradition, language, and religious practices. Some groups, such as the Huguenots (French Protestants) who immigrated during the colonial period, assimilated (同化)within one or two generations. Others, such as the German and Irish immigrants of the 19th century, still maintain some aspects of their traditional cultures.Traditionally the United States has been described as a melting pot, a place where the previous identities of each immigrant group are melted down to create an integrated, uniform society. In all of American history, immigrants who have come to the U.S. are not（）

A. for political reasons
B. for religious reasons
C. for economic reasons
D. for belief reasons