Oil. It is becoming more difficult to find and produce oil. The oil boom is over.
Oil is the least used.
gold
this fossil fuel provides about 40% of the worlds energy
yes
Yes it is a fossil fuel.
coal
No. At least not in our life time. Fossil fuels are the remains of plants and animals that died millions of years ago.
No its not a fossil fuel
No, while peat can be used a fuel, it is in the same class a wood it is not a fossil fuel. The form of coal that has undergone the least diagenesis (and is still a fossil fuel) is called "Lignite".
Uranium is not a fossil fuel and cannot be a fossil fuel.
Oil is a fossil fuel.
Fossil fuel is cheap