What is one of the ingredients of a Gibson?

A Gibson is a classic cocktail that is typically made with gin and dry vermouth, making the inclusion of a dash of dry vermouth essential. This ingredient is what distinguishes it from a standard martini, which can vary in its vermouth content. The dry vermouth adds a subtle flavor and smoothness that complements the gin, leading to the cocktail's signature taste profile.

The incorrect choices do not align with the traditional recipe or flavor profile of a Gibson. Simple syrup introduces sweetness, which is not characteristic of this cocktail's intended taste. Olive juice, while it is a key component in a dirty martini, does not belong in a Gibson. Lastly, pineapple juice introduces a fruity element that is not part of a Gibson's structure, further emphasizing the cocktail's classic gin and vermouth foundation.