Why Are People More Likely to Marry Individuals with Social

Why are people more likely to marry individuals with social and cultural backgrounds very similar to their own?

A) Parents and other family members always exert pressure to marry within the group.
B) People spend a great deal of time alone, and therefore can have few opportunities for meeting people.
C) People have greater access to individuals like themselves.
D) People develop irrational fears of out-group members and are scared to date them.