Final answer:
Bones would not form an organic fuel, unlike shale, plant roots, and trees, which all contribute to the formation of fossil fuels such as coal, oil, and natural gas due to their high organic matter content.
Step-by-step explanation:
The substance that would not form an organic fuel among the options provided is bones. Shale, plant roots, and trees all have the potential to contribute to the formation of fossil fuels, while bones are more typically associated with the formation of inorganic substances like minerals. Fossil fuels such as coal, oil, and natural gas are derived from the biomass of organic matter like plants, algae, and cyanobacteria that have been subjected to high pressure and temperatures over millions of years, transforming them into energy-dense substances. Bones typically do not form organic fuels because they are primarily composed of minerals such as calcium phosphate and do not have as high a content of organic carbon compounds needed for fuel formation.