Final answer:
Whataburger traditionally operates 24/7 except on Christmas Day, when they close to allow employees to spend time with their families.
Step-by-step explanation:
The question asks about the operating hours of Whataburger, a popular fast-food restaurant chain. Specifically, it inquires on which day Whataburger does not operate all day. The correct answer to complete the sentence is A) Christmas Day.
Traditionally, most Whataburger locations are open 24/7, but they close their doors on Christmas to allow their employees to celebrate the holiday with their families. This is the case with many other businesses as well, in acknowledgement of the widely celebrated holiday.