The correct answer is option 3: Radiation.

Radiation is the process by which heat is transmitted from the Sun to the Earth. Radiation does not require a medium to transfer heat and can occur through empty space. In the case of the Sun, it emits electromagnetic waves, including visible light and infrared radiation, which travel through space and reach the Earth. These waves carry energy in the form of heat, and when they come into contact with the Earth, they are absorbed and increase the temperature.

Conduction, which is option 1, is the process of heat transfer through direct contact between objects or substances. It occurs when there is a difference in temperature between two objects, and heat flows from the warmer object to the cooler one, until they reach thermal equilibrium.

Convection, which is option 2, is the process of heat transfer through the movement of fluids (liquids or gases). It occurs when warmer regions of a fluid rise due to a decrease in density, and cooler regions sink due to an increase in density, creating a circular flow of heat transfer.

Option 4, "Cosmic disturbances," is not a valid explanation for the process by which heat is transmitted from the Sun to the Earth. Alert - correct answer should be Radiation.