What Does the Fact That Italians, Jews, and Irish People

What does the fact that Italians, Jews, and Irish people were considered "blacks" by many people a hundred years ago suggest?

A) Dark-skinned Mediterraneans have often been confused with other races.
B) Distinctions based on race are often made on the basis of facial features, as well as skin colour.
C) Skin colour, not ethnic background, is the most important determinant of racial distinctions.
D) Distinctions based on race are arbitrary, socially constructed, and transitory.