Only two *of his scripts* were accepted by the television producers.
prepositional phrase
participial phrase
gerund phrase
infinitive phrase

The first option is correct, prepositional phrase. That's because it's a phrase that modifies the word two, and it consists of the preposition of, and his scripts which in itself is a noun phrase consisting of a possessive determiner "his" and the noun "scripts". It would be a noun phrase if it didn't have the preposition "of" in the beginning. Hope this helps. Let me know if you need additional help!