Answer:
Kelly is communicating using paralinguistics.
Step-by-step explanation:
Paralinguistic communication happens by means other than words. It takes place through gestures, facial expression, body language, tone, pitch, modulation, etc. Even without words, some type of message is being conveyed.
When we read the description in the passage, we note that Kelly is not communicating with words. Yet, Sheri knows it is safe to keep on talking, since Kelly is encouraging her with her "mmm-hmmm"'s. Kelly is basically letting Sheri know that she is interested in the conversation and that she wishes her friend to keep on speaking. She is communicating all that in a paralinguistic manner.