Final answer:
Whataburger started to accept credit cards in the year C)2000, marking a significant shift towards convenient payment methods in the food service industry.
Step-by-step explanation:
The fast-food chain Whataburger began accepting credit cards in the year C)2000.
Before this time, transactions at Whataburger were mainly cash-based.
The shift to accepting credit cards was significant because it represented the changing landscape of the food service industry where convenience and plastic money started becoming the norm.