I would definitely say B.) A smile because if you were just staring it may be rude or distracting to the speaker and a smile shows you are listening and absorbing the knowledge
that would be overworking ineffectively
A. Best the reason why it is not better (even though it sounds right) is because it says "out of the five cousins" there for we are comparing ben to five other people and he is the best.
You need a colon and period in your sentence.
