Final answer:
The adverbial phrase in the sentence is 'quite comfortably.' It provides information about how the bear lives in the forest.
Step-by-step explanation:
The adverbial phrase in the sentence is 'quite comfortably.' An adverbial phrase modifies a verb, adjective, or adverb and provides information about how, when, where, or to what extent the action is performed. In this case, 'quite comfortably' modifies the verb 'lives' by providing information about the manner in which the bear lives in the forest.
Learn more about Adverbial phrases