Endogamy is the practice of marriage within a certain group. Therefore. A is out. Polydomous has something to do with species of animals inhabiting several nests. B is out. Polygamy is having more than one partner at a time, without anyone's consent. Therefore, C is out. Exogamous has to do with marriage only permitted outside of the group, not in the group. D works, but let's check E. Monogamous has to do with marriage to only one person at a time, which is not the best answer for this question. So the answers is D: exogamous.
