Sentence1: I think yesterday was when I realized I shouldn't be a mathematician. Sentence2: I was at the grocery store, restocking for next week. Sentence3: I had bought around twenty items, and thought I was under my budget. Sentence4: When I went to check out, I was ten dollars over! 
 (A) I then realized that I was not good at math. (B) Then I knew that I was great at math!
B