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."
<span>s=ut+<span>12</span>a<span>t2</span></span><span>
s = distance
u = initial speed
t = time
a = acceleration</span>
Gregor looked up from his desk and thought about going to sleep again. He knew that the way to heal from this particular virus he’d Found himself with was not to sleep but to sit awake. While Gregor sat impatiently at his chair looking up every occasion his wife Matilda was sicker than he was and had given up trying to fight off her virus. Gregor had no knowledge of her state because the doctors suggest the speak to each other as little as possible.
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