In an outline, one of these entries is a main topic and three are subtopics. which is the main topic?

How did the spanish-american war affect american expansionism? a.) america took control of hawaii, cuba, and the pacific islands of guam. b.) america took possession of cuba and the philippines. c.) america gained control of puerto rico and hawaii. d.) america gained control of cuba, puerto rico, the pacific island of guam and the philippines.