Wood would be a source of renewable energy. Therefore, out of the following, wood is NOT a fossil fuel.
Oil, coal and natural gas are all resources made in the geological past from the remains of living organisms (fossils), meaning that they are all fossil fuels.
Because you see wood everyday on trees, it is a "fresh" source of energy that is easily replenished. A lot of time needs to pass in order for fossil fuels to be created.
Hope that helped.