The correct option is A Both A and R are true, and R is the correct explanation of A.
Natural resources can also be classified into renewable resources and non-renewable resources. Renewable resources are those that can get replenished as we use them. These resources are also called non-exhaustible resources.
In contrast, non-renewable resources cannot get replenished and hence, are called exhaustible resources. For example, fossil fuels are non-renewable resources that will get depleted in the future. This is why humans cannot depend on them for a longer time.