At which population growth rate is the coal supply on earth expected to last the longest
a. high growth
b. average growth
c. no growth
d. low growth

C. no growth

Explanation:

Coal is fossil fuel, its supply is limited and it takes millions of years to form. We humans use a lot of coal to meet our energy needs. The higher the population growth, the greater the need for energy and more coal will be taken from the earth's coal supply. One day this supply will run out as the population keeps growing.

For coal supplies available on earth to last longer would require no population growth, so our energy needs would not grow as it would be equal to the size of the population we now have.