Final answer:
The answer is A. slowly, which is the adverb needed to correctly complete the sentence and describe how to drive after the storm.
Step-by-step explanation:
The correct answer to the question "The meteorologist urged everyone to drive _____ after the storm" is A. slowly. In this sentence, an adverb is needed to describe how the meteorologist is suggesting everyone should drive. Adverbs modify verbs, adjectives, or other adverbs, and in this case, 'slowly' is modifying the verb 'to drive', indicating the manner in which the action should be performed. The other options do not grammatically fit the sentence. 'Slow' is an adjective, which would typically be used to modify nouns, not verbs. 'Slowest' is a superlative adjective, which is not appropriate in this context. 'Slowing' is a verb form, and it does not serve the function of an adverb describing how to drive.