How many hours are there in a day?

A day is defined as the period it takes for the Earth to complete one full rotation on its axis relative to the sun. This duration is standardized as 24 hours. This definition is universally accepted across most cultures and is essential for organizing time systems globally, including timekeeping and scheduling.

The concept of 24 hours being a day is also crucial in various fields, such as astronomy, physics, and everyday life, ensuring that there is a common framework for measuring time consistently. In contrast, the other choices do not align with this universally accepted definition, as they represent durations that do not correspond to the rotation of the Earth.