Marriage outside of one's racial-ethnic group

I am trying to answer a question that maybe you can help with, it is:

A marital couple in which one spouse belongs to a given racial-ethnic group and the other spouse belongs to a different racial-ethnic group is?

a) Mixed marriage.
b) Multicultural marriage.
c) Open Marriage.
e) Endogamous marriage.

I can immediately rule out (e) as it relates to marriage inside the same social group. Actually in my opinion Exogamy would be the correct answer but it is not an option. So the 2 possible answer I am torn between are (a) mixed marriage and (b) Multicultural marriage.