Translate the following paragraph into Chinese Rational people know that decisions in life are rarely black and white but usually involve shades of gray. At dinnertime, the decision you face is not between fasting( 斋戒 ) and eating like a pig but whether to take that extra spoonful( 一匙之量 ) of mashed( 捣烂 ) potatoes. When exams roll around( 再次发生 ) , your decision is not between blow ing them off( 逃避 ) or studying 24 hours a day but whether to spend an extra hour reviewing notes instead of watching TV. Economists use the term marginal changes to describe small incremental ( 递增的 ) adjustments( 调整 ) to an existing plan of action. Keep in mind that margin means “edge”, so marginal changes are adjustments around the edges of what one is doing. Rational people often make decisions by comparing marginal benefits and marginal costs .