How Did John Alan Lee Identify the Six Different Ways

How did John Alan Lee identify the six different ways to love,which he called "colours" of love? 

A)  He asked college students to identify feelings associated with their most recent romantic relationship. 
B)  He interviewed couples who had been married for 20 years or longer. 
C)  Using lists of feelings words, he asked individuals between the ages of 10 and 95 to identify the words they most associated with feeling loved. 
D)  He collected statements about love from works of fiction and nonfiction including both ancient and modern authors.