Sorry taking educated guess but from my perception it's b but ??????
Bob is just a human like us and feels stuff, its probaly due to his environment and pressures/stress but heck who really knows. Bob is Bob. and that is that.
I would think its A. the rest of the options are for people that can stand still and focus.
Answer:
Because it does. No other answer. This is one of those Impossible to Answer questions from college.
