Identify the word or words that the underlined phrase modifies. Not surprisingly, the pool in their backyard draws all the neighborhood kids (Underline "in their backyard")

The answer is "the pool."

The expression "in their backyard" is a prepositional phrase, which modifies the noun before it.

Prepositional phrases are words arranged without a subject or verb. They are usually made up of either a preposition and a noun, a preposition and a gerund, or a preposition and a clause.

If prepositional phrases modify a noun, as in this case, they are called "adjectival phrases."