Whether the Spanish Word Casta Should Be Translated "Caste" or "Class

Whether the Spanish word casta should be translated "caste" or "class" or "race" or "ethnic group" is an interesting question because

A) The original "estates" whose interbreeding produced the castas were defined in terms of race.
B) As Spaniards monopolized wealth, power, and prestige in Mexico, they could be viewed as the ruling class, with everyone else making up the subject class.
C) Members of the original colonial estates differed from one another in culture, so they might be seen as constituting separate ethnic groups.
D) All of the above.