How does the heat energy from the sun reach us through the vacuum of space?

a. conduction

b. radiation

c. convection

d. none of the above choices are valid

Physically between the sun and the Earth there is only emptiness. Methods of heat conduction require a means to transport it either by convection or conduction. In the absence of this, said methods cannot be used. The third method is radiation, which precisely does not require any means for its 'transport'.

In this way the only form of heat transfer is through radiation. The correct answer is B.