You are correct! Statement B is indeed the one that is best supported by the theory of evolution.
The theory of evolution, particularly natural selection, posits that individuals with characteristics that are better suited to their specific environment are more likely to survive and reproduce. This can lead to those advantageous traits becoming more common in the population over time. Statement A, on the other hand, suggests a universal advantage in all environments, which does not align with the idea that traits can be advantageous in some contexts but not in others.