Which of the following statements about wind energy is not true?

a. Wind energy is a nonrenewable energy resource.

b. Wind energy is used to sail ships.

c. Wind energy is not reliable.

d. Windmills are currently being used to provide energy.

So we want to know what is not true for the following statements about solar energy. It is true that it is used to sail ships. It is true that is not reliable. It is true that windmills are used to provide energy from wind. But it is not true that wind energy is a nonrenewable energy resource. So the correct answer is a.