How Does the Decline in Satisfaction in a Relationship Compare

How does the decline in satisfaction in a relationship compare in married and cohabiting couples?

A) Both kinds of couples experience identical rates of decline in satisfaction.
B) Cohabiting couples experience the decline in satisfaction later in the relationship than do married couples.
C) Cohabiting couples experience a slower decline in satisfaction than do married couples.
D) Cohabiting couples experience a steeper decline in satisfaction, and it occurs earlier in the relationship.