Why do most people choose to specialize in a narrow set of skills for their work, rather than to learn a little bit about several varied fields of endeavor?

A) They feel that doing so will minimize their chances of being unemployed.
B) They don’t correctly perceive the costs of being so specialized.
C) It allows them to earn more income by being more productive.
D) They are unaware of how much better off they would be if they diversified their skills.