d. the tendency to choose a mate with similar personal characteristics.
Explanation:
Endogamy was common in ancient times to preserve the blood, the similarities between the members of the family, and the dynasties. However, this practice was dangerous because of the possibility of creating a generation of members with some kind of genetic disease or malformation.
Vocalizations like "uh huh," "oh," and "umm" that encourage others to continue speaking or indicate that we would like to speak are called Back-channel cues.
