Which of the following is a primarily hop-derived flavor?

The flavor profile of beer is significantly influenced by the variety of hops used during brewing, and certain flavors are distinctly derived from hops. Pine is one of the flavors that hops can impart, particularly from certain hop varieties like Chinook and Cascade. This pine-like character is often associated with beers that have a significant hop presence, especially in American-style IPAs and pale ales.

In contrast, other flavor options like citrus, caramel, and chocolate, while they can appear in various beers, are typically linked to different sources. Citrus flavors can come from certain hop varieties as well, but they are not primarily defined by hops when compared to the stronger sap-like, resinous character that pine provides. Caramel flavors typically result from the malt used in the beer, particularly when malts are kilned to develop rich, sweet flavors. Similarly, chocolate flavors are derived from darker malts and other ingredients rather than hops.

Thus, pine is clearly a flavor that is primarily associated with hops, establishing it as the correct answer in this context.