Answer:
Loosened.
Explanation:
Participles are words that are formed from a verb, but acting as a noun or adjective in the sentence. They are used in sentences to modify the verbs or nouns, or the noun/verb phrases.
Loosened rocks may tumble down canyons when it is raining heavily
In the above sentence, "loosened" is a verb in itself but when put along with a noun "rocks", it acts as an adjective. So, it becomes the participle in the sentence. It changes the nature of the noun "rocks".
