Final answer:
The adverb in the sentence 'Ralph ran rapidly' is rapidly.
Step-by-step explanation:
The adverb in the sentence 'Ralph ran rapidly' is rapidly. Adverbs are words that modify verbs, adjectives, or other adverbs and typically end in -ly. In this sentence, 'rapidly' modifies the verb 'ran' and describes how Ralph ran.
Learn more about Adverbs