What is the disadvantage of burning fossil fuels?

The disadvantages of burning fossil fuels are:

a)Fossil fuels have had a good run, but they’re on their last legs.

b)Fossil fuels release carbon dioxide when they burn, which adds to the greenhouse effect and increases global warming.

c) Combustion of fossil fuels releases acidic gases.

d)The burning of fossil fuels produce smoke and leaves behind a lot of ash.