What substance is often associated with sulfur odors?

Hydrogen sulfide is known for its distinct, unpleasant odor commonly described as resembling that of rotten eggs. This compound is associated with sulfur and is often produced through the decomposition of organic matter, as well as in various industrial processes. Its presence can cause serious health issues due to its toxicity at higher concentrations.

In contrast, carbon dioxide is a colorless and odorless gas that does not have any sulfur compounds in its makeup. Methane, primarily a natural gas, is also odorless and does not have the sulfur characteristics associated with hydrogen sulfide. Ammonia has a strong, pungent smell but is not related to sulfur; its odor comes from nitrogen compounds. Therefore, hydrogen sulfide is the substance most directly linked to sulfur odors, making it the clear choice.