Final answer:
The underlined modifier "quickly" is an adverb that modifies the verb "drove".
Step-by-step explanation:
The underlined modifier in the sentence "Sally drove quickly to the hospital" is an adverb.
An adverb modifies a verb, adjective, or another adverb. In this case, the word "quickly" modifies the verb "drove," indicating the manner in which Sally drove.
For example, you could rewrite the sentence as "Sally drove fast to the hospital."
Learn more about Parts of Speech