Final answer:
Gerund phrases cannot be used to form an adjective complement because they function as nouns and do not provide adjectival information to complement an adjective.
Step-by-step explanation:
The adjective complements in English grammar. Adjective complements are words or phrases that complete the meaning of an adjective. These can be prepositional phrases, infinitive phrases, or noun clauses. An adjective complement usually follows the adjective it is complementing and provides additional information about the object or subject of the sentence.
Gerund phrases generally function as nouns, rather than providing the necessary adjectival information that would complement an adjective. Therefore, gerund phrases cannot be used effectively as adjective complements as they do not perform the same modifying or descriptive function that complements the adjective.
For example, in the sentence "The movie is interesting to watch," the prepositional phrase "to watch" acts as the adjective complement, providing more information about the adjective "interesting." However, a gerund phrase like "watching the movie" would not function as an adjective complement because it does not modify or directly complement an adjective.