Why is using fossil fuels considered unsustainable?

Fossil fuels take millions of years to replenish

Fossil Fuel is limited it is like coal there is a limit and it won't last forever. This also contributes that it is not safe for the environment as well as the safety and health of people. This is similar to when there are many factories around an area there is going to be a high percentage of respiratory diseases such as asthma.

i believe it is b. what was the cause of the big bang

hope this !

energy can be converted from one form to another, but it cannot be created or destroyed in ordinary chemical or physical means. do not understand what you are asking but hope this