Jacinta Is Playing a Game on Her Cell Phone Where

Jacinta is playing a game on her cell phone where she has to identify words from a list of six letters. On level 49, she has found all but one word and she simply cannot see what she is missing. She puts the phone down, and three hours later picks it up and immediately sees that she missed the word "portal." The time away from the problem that allowed her to come up with the answer was called

A) decomposition.
B) incubation.
C) reformulation.
D) a heuristic period.