The internal structure of an adverb phrase allows for pre-modification and post-modification, usually to express degree or intensity. Analyze the following statements regarding the constituents of an adverbial phrase:

I. An adverb phrase can be modified by another adverb, as in "quite remarkably," where "quite" functions as a pre-modifier.
II. Post-modification in an adverb phrase is extremely rare but can occur with the adverb "enough," as in "well enough."
III. Adverb phrases function exclusively as adjuncts and can never perform the role of a subject complement in an English sentence.

Which of the following are CORRECT: