The correct option is D a man with a gun
A phrase is a group of words which makes a clause without using a subject and a verb. Option D)a man with a gun is correct as man is a noun here and with a gun is a prepositional phrase functioning as a post modifier. The other options are wrong as a noun phrase cannot have a subject, a verb, or a phrasal verb(looking for). The correct answer is D)a man with a gun.