Which fortified wine from Portugal is recognized for its sweetness, high alcohol content, and flavors of black fruit?

The fortified wine recognized for its sweetness, high alcohol content, and rich flavors of black fruit is Port. This wine originates from the Douro Valley in northern Portugal and is commonly associated with various styles, primarily Ruby and Tawny Port. Ruby Ports tend to showcase vibrant, fruity flavors, while Tawny Ports are aged and can have more complex notes of nuts, caramel, and dried fruits.

Port is specifically known for its fortification process, which involves adding grape spirit to stop fermentation early. This retains a significant amount of natural sugars, resulting in the wine's characteristic sweetness and elevating its alcohol content typically between 18% to 20%.

The other options have distinct characteristics and do not align with the description given. Sherry, while a fortified wine from Spain, is often dry and varies widely in flavor from nutty and oxidized to fresh. Rioja is a region in Spain primarily known for its red table wines, and Sauternes is a sweet white wine from France made primarily from Sémillon grapes affected by noble rot, which sets it apart from the black fruit flavors of Port.