If Debra turns down the full-time position at Burger Hut, what is the most reasonable economic explanation for her decision?

The most likely reason for any person turning down a full-time job is money.

It is more likely than not that Burger Hut was unable to provide compensation for Debra's services at a rate that a. Debra felt appropriate or b. Debra felt was necessary to make accepting the job worthwhile.

For instance, if Debra lived far away from the Burger Hut than any job would need to pay enough to partially cover the cost of her commute in addition to living and (hopefully) saving money.

D) The incentive of making more money now with the full time job is outweighed by the long term benefit of going to college and investing in human capital. Debra will earn a higher salary over her life with a degree in business than working full time at Burger Hut.