Which of the following Belgian beer styles is most likely to exhibit assertively sour, acidic flavors?

Flanders red ale is a Belgian beer style known for its distinctive sour and acidic flavors. This style typically undergoes a mixed fermentation process, involving both yeast and lactic acid bacteria, which contributes to its characteristic tartness and complexity. Flanders red ales are often aged in oak barrels, which further enhances their sour profile and adds layers of flavor such as fruitiness and oak character.

The other styles listed do not typically exhibit the same level of sourness. Dubbel is a malty, dark beer with a fruitiness and sweetness, but it lacks the acidity associated with Flanders red ales. Saison, while possibly having some fruity and spicy notes, does not generally reach the sour levels found in Flanders red ales. Witbier is a Belgian white beer that is light and refreshing, often flavored with spices like coriander and orange peel, but it is also not sour or acidic. Thus, the characteristics of Flanders red ale clearly align with the question regarding assertively sour, acidic flavors.