In the sentence 'The club meeting will be in an hour,' the phrase 'in an hour' functions as

• A. Adverbial
• B. Noun phrase
• C. Prepositional phrase
• D. Adjective clause

Answer: (A)

Time expressions that tell when something happens function as adverbials. Here, "in an hour" tells when the club meeting will take place, answering the question "When will the meeting be?" and thus modifying the verb phrase "will be" (the action of the sentence) or the whole predicate. Although it is formed as a prepositional phrase (in + an hour), its role in this sentence is adverbial, specifying time. It isn’t a noun phrase or an adjective clause, since it doesn’t name a thing or describe a noun, and there’s no clause structure involved.