The formal structure that best describes a sonata is "classical."
A sonata typically follows a three-part form known as sonata-allegro form, which includes an exposition, development, and recapitulation. However, "classical" is the overarching term that encompasses this structure in the context of classical music compositions.
If you are looking for the specific form associated with sonata movements, it would be best to refer to "sonata-allegro" form specifically, though it wasn't one of the provided options.