The "melting pot" theory of american society assumes that immigrants
a. are ethnocentric
b. cook better than native-born americans
c. become steelworkers
d. assimilate into a single american culture

The melting pot theory of american society assumes that immigrants assimilate into a single american culture.

Explanation:

First of all the melting pot theory is a concept of integration and understanding. It means that all backgrounds form a single context and that all of the cultural differences immigrants brought to the American Culture define the American Culture as a wide multicultural society that values, recognizes and impulses each one's beliefs, acts, and uses. in second place, the melting pot theory also states that all cultures are mixed and find the freedom to keep their essence. The American society is one of the best cases of multicultural integration and coexistence.

the answer would be:

b. race