Final answer:
The sentence is not a compound sentence because it lacks two independent clauses joined by a coordinating conjunction or a semicolon. It is a simple sentence with a compound verb.
Step-by-step explanation:
The sentence "I put a ring on my finger and a necklace around my neck" is not a compound sentence, because it does not contain two or more independent clauses joined by a coordinating conjunction or a semicolon. Instead, this sentence has a single subject performing two actions, which makes it a simple sentence with a compound verb.
To be considered a compound sentence, it would need to have two distinct parts that could stand alone as sentences. For example, a proper compound sentence could be "I put a ring on my finger, and she placed a necklace around my neck." Here, the two clauses "I put a ring on my finger" and "she placed a necklace around my neck" are joined by the coordinating conjunction 'and', each clause having its own subject and verb, making it a compound sentence.