Which One of the Following Examples Most Clearly Illustrates the Role

Which one of the following examples most clearly illustrates the role of retrieval in problem solving?

A) Phillip is trying to solve a physics problem on a class exam.He is so anxious that he cannot remember how to do the problem.
B) Aaron is trying to solve a problem on his physics test, but he was absent the day his teacher talked about such problems.
C) Charlie is doing a series of addition problems.He overlooks the subtraction sign on the last problem, so he adds when he should subtract.
D) Matthew is angry that another boy stole his bicycle, and so he steals a bicycle from someone else.