What's the preposition phrase in the sentence Corn, Beans, squash were three of the most important crops

The preposition phrase is "of the most important crops".

Explanation:

A preposition phrase is a group of words or phrases that begins with a preposition and contains an object and any word that modifies it. Added to that, preposition phrases also modify a noun or a verb, depending on the sentence.

In the given sentence, the preposition is "of" which also makes it easier for us to identify the preposition phrase.

Thus, the preposition phrase is "of the most important crops".

in the quotation from passage, connie willis states that literature is a way for authors from the past to communicate with readers of today. we can read their stories, books, and other texts to learn lessons about life. willis refers to these lessons as messages “from beyond the grave.” willis has a favorable viewpoint about the timelessness of literature.