Because wind turbines supply no energy on windless days, and solar power is only generated when the sun is up and out, one inherent problem with both wind and solar power is the

A) government subsidy problem.
B) zero-emissions problem.
C) energy storage problem.
D) oil-complementarity problem.

Energy Storage Problem

Refers to the challenge of capturing energy produced at one time for use at a later time, important for renewable energy sources that don't produce power continuously.

Wind Turbines

Mechanical devices that convert wind energy into electrical energy.

Solar Power

Energy from the sun that is converted into thermal or electrical energy, considered a renewable and clean source of power.