Which of the following regions is most likely to have gravel topsoil?

The region known for its gravel topsoil is Pauillac, located in the Bordeaux wine region of France. This area is characterized by its well-draining gravelly soils, which are ideal for growing high-quality grape varieties, particularly Cabernet Sauvignon. The gravel allows for good drainage while retaining heat, which benefits the ripening of grapes.

Other regions listed in the choices have different soil compositions. For instance, the Douro Valley in Portugal is known for its steep terraced vineyards and schist soils, which are primarily composed of slate. The Mosel region in Germany features predominantly steep, slate-based soils that capture warmth and provide excellent drainage, but do not have gravel. Priorat in Spain has a unique soil called licorella, made of decomposed slate and quartz, which contributes to the region's distinctive wines but is not gravel. Thus, Pauillac stands out for its gravel topsoil, which plays a crucial role in its viticulture.