How many hours are in a day?

A day is defined as the period of time it takes for the Earth to complete one full rotation on its axis. This rotation takes approximately 24 hours, which is the basis for our standard measurement of a day. This time frame is universally accepted across most cultures and is fundamental in various contexts, from daily activities to scientific calculations.

In addition to this, this 24-hour period is divided into two segments: 12 hours of daylight and 12 hours of nighttime, although this can vary depending on the time of year and geographic location. Hence, 24 hours represent the complete cycle of day and night, making it the correct answer in this context.