What distinguishes brown stock from white stock?

Brown stock is characterized by the process of browning or roasting the bones before they are simmered. This initial step enhances the flavor and color of the stock, adding a rich, deep, and roasted taste that is distinct from that found in white stock, which uses uncooked bones. The browning process caramelizes the natural sugars in the bones, resulting in a more complex and robust flavor profile.

While the other options might describe characteristics of stocks, they do not specifically differentiate between brown stock and white stock as effectively. Fish bones typically refer to fish stock, and while vegetables are used in both types of stock, they are not a distinguishing factor between the two. Additionally, the length of simmering can vary for both types of stock and is not a defining characteristic. Therefore, the roasting of bones is what primarily sets brown stock apart from its white counterpart.