Answer: c) para language
Step-by-step explanation:
Para-language is the language tat is used for conveying message or communication of emotion or modifying meaning through intonation technique, pic factor, volume factor , prosody etc.It is also known as vocalic.
According to the question,para language is used when a person tend to decrease their volume or tone of speaking through soft speaking as to decrease effectiveness of communication.
Other options are incorrect because example of kinetics, meta-language and proxemics is not displayed through case.Thus, the correct option is option(c).