Concept:The earth's revolution is its orbital motion around the sun, which gives rise to the yearly calendar.Explanation:The earth takes about 36541 days to complete one revolution around the sun.This fixed period of revolution is what we measure as a year.Day and night, dawn and twilight, and apparent sunrise and sunset are all caused by the earth's rotation on its axis, not by revolution.Therefore, among the given options, the direct effect of the earth's revolution is that it determines a year.Answer:B. It determines a year