What are the combustible components of coal?

The combustible components of coal primarily consist of carbon, hydrogen, and sometimes sulfur. Carbon is the main component and is responsible for the energy content of coal, providing the heat when burned. Hydrogen also contributes to the energy release during combustion. Sulfur can be present in varying amounts depending on the type of coal and is important to note because it has implications for emissions when coal is burned; while it's not a major contributor to the heat produced, it does contribute to environmental concerns.

When considering the other components mentioned in the choices, nitrogen, oxygen, phosphorus, and helium, these do not play a significant role in the combustion characteristics of coal. Nitrogen and oxygen are present but are part of the reaction process, while phosphorus and helium are not relevant to the primary combustion chemistry of coal. Thus, the combination of carbon, hydrogen, and sulfur provides the most accurate description of the combustible elements in coal.