Some of the information needed for the question is not given. However, I know this question and the additional information that was needed. On the tree branching diagram the diagram should be labeled as B on the first spot, A on the second spot, and C on the third spot. Now, it can also be labeled A on the first spot, B on the second spot, and C on the third spot. Either will be correct, but I think B-A-C is the better choice.