Answer-
A pro to using fossil fuels is, because it is cheap and reliable,fossil fuels are cheap and reliable sources of energy. They are excellent types of fuel to use for the energy base-load, as opposed to some of the more unreliable energy sources such as wind and solar. Another Pro is that, they are well developed,the technology we use to harness the energy in fossil fuels is well developed. The main reason for this is that fossil fuels have been used to power our world for many decades.
On the other side there is also some cons on fossil fuels. A con on using fossil fuels is that, they contribuate to global warming. Fossil fuels are not green sources of energy. In fact, they contain high amounts of carbon and have been blamed for being the main contributor to global warming. The last con is, fossil fuels are non-renewable energy sources. This means that there is a finite amount of fossil fuels available and the reserves are not replenished naturally.