Concept:The variation in the length of day and night is linked to the Earth’s yearly orbit around the Sun while its axis stays tilted.
Explanation:Rotation of the Earth causes day and night, but it does not make their lengths vary throughout the year.
During revolution, the Earth moves around the Sun with its axis tilted at about
23.5∘.
As the Earth revolves, different parts of the planet receive different amounts of sunlight at different times of the year.
This causes days and nights to become longer or shorter depending on the season.
Therefore, the movement responsible for the variation in the length of day and night is revolution.
Answer:B. revolution