Final answer:
The adverb in the sentence is 'angrily'.
Step-by-step explanation:
The adverb in the sentence is angrily. An adverb is a word that modifies a verb, adjective, or other adverb. In this case, 'angrily' modifies the verb 'fought' and tells us how the bear fought. Other examples of adverbs include 'quickly', 'slowly', 'happily', etc.
Learn more about Understanding adverbs