Question

coal is a very dirty fossil fuel, but there are several advantages to using coal as a fuel source. for example, coal is energy dense and it is easy to transport. what is another advantage of coal production? it is cheap. it produces no air pollution.

Explanation:

Coal is a fossil fuel. One of its advantages is that it is relatively inexpensive compared to some other energy sources. While it is a dirty fuel (contradicting the claim of "produces no air pollution"), the question asks for an advantage of coal production. Being "cheap" is a valid advantage as it can make energy more accessible and affordable in some contexts.

Answer:

It is cheap.