Answer:
The correct answer is C) People respond to incentives.
Step-by-step explanation:
People respond to incentives is the fourth principle in Economics. For this particular case, adding tax to unhealthy food is a disincentive to buy it and at the same time an incentive to buy healthy food. This happens because incentives make people act, in a positive or negative way towards a certain product, and because rational people use cost and benefit comparisons to buy something.