The sun making your skin feel warm is heat transfer by

A. convection

B. reflection

C. radiation

D. conduction

It is radiation because radiation is transfered by ultra-violet rays.

C. radiation

Convection is the direct heat transfer from a fluid. Air is a fluid.

Radiation is the transfer of heat energy through empty space.

Conduction is the direct heat transfer from one substance to another.

Reflection is the throwing back by a body or surface of light, heat, or sound without absorbing it.