Answer:
monogamous
Explanation:
     "Monogamous" is a term used when people have only partner. They date, is married to or have sexual relationship with only one person at a time.
     England's research have found that relationship is very weak among college students. They have found out that students generally hook up rather than to be in a relationship.
     But dating has a meaning and it leads to a relationship which may be consider as a relationship with one person at a time.
Thus the answer is "monogamous".