What is prepositional phrase New trade routes were developed by the Vikings.?

The prepositional phrase in the sentence "New trade routes were developed by the Vikings" is "by the Vikings".

Here's why:

* Prepositional phrases begin with a preposition (in this case, "by") and are followed by a noun or pronoun (in this case, "the Vikings").

* They function as adverbs, modifying the verb "developed" by telling us who performed the action.

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