Answer:
The adverb in the sentence is "madly", which modifies the verb "ran" and describes how Robinson Crusoe ran about on the island.
Step-by-step explanation:
An adverb is a word that modifies or describes a verb, an adjective, or another adverb in a sentence. In the given sentence, the word "madly" modifies the verb "ran", which means it describes how Robinson Crusoe ran.
To identify an adverb, you can ask questions like "How did Robinson Crusoe run?" In this sentence, the answer to that question is "madly", which tells us that "madly" is modifying the verb "ran". Therefore, "madly" is the adverb in the sentence.