The correct answer is D) uneven heating of Earth's surface by the Sun.
Indeed, the solar radiation hits the surface with different angles between the equator and the poles: the angle the light rays form with the vertical line above a position is 90° at the poles, 23° at the tropics and 0° at the equator (see picture attached).
Moreover, the vegetation that can be found in the tropical zones absorbs most of the radiation, while, for example, the ice at the poles reflects it almost all into space.
For these reasons, tropics have the highest solar radiation, while the poles have the lowest. The difference in solar radiation creates air movement (winds) from the warmer to the cooler areas. Hence, Earth has winds going from the tropics towards the poles and towards the equator, as your diagram shows.