The correct answer is "body language".
Body language is a nonverbal communication system, which aims to transmit messages using physical behaviour instead of words. It consists on facial expressions, postures, gestures, eye movements, touching practices, etc. Many times, it involves involuntary expressing and can even convey a message which contradics what is said using words. This is why, for example, the police develops techniques to uncover liars.
Proxemics are not applicable here, as they refer to the study of how humans use the space and about the consequences generated by population density. Chronemics studies how timing affects communication. Finally, artifacts are anything which has been artificially created by mankind and which contains information about the cultural chracteristics of its producer or users.
