Answer:
Walked - C. Verb
Slowly - D. Adverb
Step-by-step explanation:
Actually, I selected the above this way because the question did not indicate the particular part of speech. You can find the correct answer in the above.
A verb is known to be an action word or a doing word. "Walked" as used in the sentence is a verb because it tells what the pronoun "I" is doing.
Also, the adverb modifies and explains what the verb is doing.