Coal reserves are said to be enough to last for another hundred years. Do you think we need to worry in such case? Why or why not?

Yes, this is a case of concern as coal is one of the important fossil fuels and it takes millions of years to be formed. This is also an exhaustible natural resource so we have to use it judiciously so that it can be available for our future generations as well. If we will go on consuming it at a faster rate then it might get exhausted very soon as the rate at which it is formed is very slow.