Explanation:

There is a difference between the solar energy received and solar energy circulated (which affects the temperature of a region). All the factors from options A to C only circulate the solar energy that is already received by the earth; they do not as such directly affect the solar energy incident on earth. There is a minor case for the cloudiness created by movement of ocean currents or winds that often blocks solar insolation; but the major cause for variation is earth’s curvature.