The most likely reason for the change in price over time, where microwaves in 1985 would be $585 in today's dollars after adjusting for inflation, is:
d. The price of microwave ovens has shifted to match the cost of living.
This means that the price of microwave ovens has adjusted over time to reflect changes in the overall cost of living, inflation rates, and economic conditions. Adjustments like these are common to ensure that the cost of goods remains affordable and competitive relative to other expenses consumers face.