Does this sentence contain a prepositional phraseLast year our neighbors adopted huge golden retriever named Sparky?

Yes, the sentence "Last year our neighbors adopted a huge golden retriever named Sparky" contains a prepositional phrase: "named Sparky".

Here's why:

* Preposition: "named"

* Object of the preposition: "Sparky"

The prepositional phrase acts as an adjective modifying "retriever", telling us the retriever's name.