Which of the following is a key ingredient in Champagne?

The correct choice is Pinot Noir grapes, which are one of the primary grape varieties used in the production of Champagne. Champagne is produced in the Champagne region of France and is primarily made from three main grape varieties: Chardonnay, Pinot Noir, and Pinot Meunier.

Pinot Noir is particularly significant because it contributes to the structure and body of the Champagne, enhancing its complexity and depth of flavor. This grape variety brings characteristics ranging from red fruits, cherries, and spicy notes to the resulting sparkling wine.

The other grape varieties listed—Cabernet Sauvignon, Merlot, and Zinfandel—are not used in the production of traditional Champagne. While they are popular in red wine production, particularly in regions like Bordeaux and California, they do not play a role in the unique process or style of true Champagne. As such, Pinot Noir stands out as the correct choice in this context.