In this answer choice, we effectively have two columns. In the first column is simply R and B, with R over B. This represents spinning either red (R) or blue (B).
Depending on the outcome, you branch the same outcomes from that.
So if you spin R, then you'll have R and B branch off that. Same idea applies to blue as well.
Something like choice D doesn't work because we have R show up twice at the very bottom.
