Answer:
Nonverbal.
Step-by-step explanation:
Nonverbal is a form of communication in which language is not used. The message is conveyed through gestures, symbols, and non-word vocal.
Experts have studied that most of our communication is nonverbal. We do not always use language to convey our message.
An example of nonverbal communication is depicted in the question. The reply of Gretchen to Fanny's points is a form of nonverbal response. Gretchen did not say a word to convey the message that she agrees with the points of Fanny but she nodded.
In the question, Gretchen's nodding is a form of nonverbal response that conveys the message 'Yes.'
So, the correct answer is nonverbal.