Which of the following Belgian beers is always made with wheat?

Witbier is a style of Belgian beer that is distinctively brewed with a significant amount of wheat, which is an essential characteristic of the style. This is unlike other types of Belgian beers listed in the question, such as Belgian Blond Ale, Dubbel, and Tripel, which primarily use barley malt.

Witbier is traditionally brewed with a mix of barley and at least 30% unmalted wheat, contributing to its light, smooth body and hazy appearance. It is often flavored with spices, typically coriander and orange peel, which enhances its refreshing qualities. The wheat used in Witbier not only influences the flavor but also affects the mouthfeel, giving it a creamy texture that is a hallmark of the style.

In summary, the unique reliance on wheat in its recipe defines Witbier, making it the correct answer in comparison to the other options, which do not have wheat as a necessary ingredient.