Which two examples may be converted into fossil fuel after being buried under pressure for a long period of time

I would say that two products of the earth are coal and petroleum and when they are burned say in a car or a power generating facility they can be converted to fossil fuels. The burning of these fossil fuels are causing too much greenhouse gases and making the earth's temperature rise and resulting in more extreme weather so fossil fuels need to be phased out so the earth will remain inhabitable for humans.