Solar power is a renewable resource because
a. it is continually replenished
b. using the resource consumes it
c. it can be found everywhere on earth
d. all of the above

The correct answer is a - it is continually replenished.

Renewable energy is said to be any energy source that is naturally replenished , such as that derived from the sun (solar), wind, geothermal or hydroelectric  action. Also energy produced from refining of biomass is often placed in the class of renewable energy.

Renewable energy source is from an energy source that is replaced  by a natural process at a rate that is equal to or faster  than the rate at which that resource is being consumed.

Solar energy handsomely fulfils these descriptions. It is natural, inexhaustible and more than enough to sustain the earth for millions of years yet.