In the Typical Long-Term, Romantic Relationship, a Couple Will Experience

In the typical long-term, romantic relationship, a couple will experience passionate love for ____.

A) three months or so-six to nine months at the most
B) a year or so-two or three years at the most
C) seven years or so-ten to fifteen years at the most
D) an unlimited number of years or decades, if the relationship is successful