Married People Tend to Live Longer Than Unmarried People

Married people tend to live longer than unmarried people.It could be that they take better care of themselves when they have the responsibility of a family.It could also be that:

A) people who are healthier are more likely to get married.
B) people who are married have less sex,so they are less likely to contract sexually transmitted infections.
C) unmarried people are more likely to travel to areas of the world where there are higher rates of diseases.
D) unmarried people are less likely to have sex and are therefore more depressed,leading to physical ailments.