Traditionally most units of time are based upon a)the motions of earth, b)the longitude of an observer, c)the motions of the moon, or d)the real motions of the sun

The correct answer is option A (the motions of Earth).

Explanation:

The word "Time" may have different meanings, "Time" in a simple term, it is used to measure events, and it is the bedrock that is used to determine seasons. Time is measured in seconds, minutes, hours, days, weeks, months, years. Unlike clocks, and other different devices used to measure time, these devices were not available some centuries ago. So, time was measured in those centuries with the help of the knowledge of the rising and setting of the sun which are caused by the rotation of the Earth. The most standard unit of time used this day are all products of research Astronomers were able to do through studying the motions of the Earth. For instance, when the Earth makes a full rotation around its own axis, that signifies a day, which is a period of about 24hours. considering we have leap years, so it is not complete 24 hours.

this is a good question! i'll do some research and come back when i have the answer!