The question is testing the understanding of basic vocabulary related to communication. The correct answer is 'D. Nonverbal' because nonverbal communication refers to the transmission of messages without the use of words, which is the direct opposite of verbal communication. Option A is incorrect because verbal communication involves the use of words. Option B is incorrect because oral communication specifically refers to spoken words, not necessarily non-verbal cues. Option C is incorrect because silent communication is not a standard term used to describe non-verbal communication.