Which of the following affects the aromatic profile of beer the most?

The aromatic profile of beer is significantly influenced by the sourcing of hops. Hops are responsible for the primary aromatic components in many beers, providing a wide range of scents and flavors from floral and citrus to herbal and piney. Different hop varieties contribute distinct aroma characteristics, and the location where hops are grown can also impart unique terroir elements to the beer.

While the type of yeast used can also affect beer's aroma, particularly through the production of esters and phenols during fermentation, it generally plays a secondary role compared to hops in styles that rely heavily on hop aroma. Alcohol content can influence overall perception but does not directly alter the aromatic compounds themselves. The water profile can affect mouthfeel and how flavors and aromas are perceived, yet it has a minimal direct impact on the specific aromatic elements compared to the hops used. Thus, sourcing of hops stands out as the most significant factor affecting the aromatic profile of beer.