The retired government official spoke knowledgeably about foreign policy and international trade. Read more about Adverbs.
Adverb is a word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc.
Therefore, in the above question, the correct answer option C. knowledgeably modifies the verb spoke.
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