Final answer:
The compound found in all living matter, fossil fuels, and charred candlewicks is carbon (C). It is essential for the formation of organic molecules and for fuel after being stored as fossilized carbon.
Step-by-step explanation:
The substance that is a compound of all living matter, including fossil fuels, and is the same black material found on a charred candlewick, is carbon (C). Carbon is the fourth most abundant element in living organisms and is present in all organic molecules. It plays a crucial role in the structure of macromolecules and is vital for living organisms. Carbon compounds from plants and algae, under high pressure and over millions of years, have formed fossil fuels such as coal, oil, and natural gas, which humans use as fuel. As these fossil fuels are burned, the increase in carbon dioxide in our atmosphere contributes to climate change, making it a significant environmental concern.