Communication through gesture is related to

The correct answer is A) Kinesics. Kinesics is the study of body movements that carry meaning, including gestures, posture, facial expressions and eye movement. Ray Birdwhistell introduced the term in the 1950s, and it sits within the wider field of non-verbal communication.

Why the others do not fit:

• Proxemics studies the use of personal and social space during interaction. Edward T. Hall introduced the term.
• Para-language (paralinguistics) concerns vocal features such as pitch, tone, pace and volume, not body movement.
• Non-verbal behaviour is the umbrella category. Gesture falls under it, but the question asks for the specific discipline that studies gesture, which is kinesics.

Connection to the syllabus: communication and interpersonal skills feature in GS-IV ethics and in Mains answers on leadership and public administration, where an officer's body language shapes how citizens perceive them.

Trap: choosing D because gesture is clearly non-verbal. That is true but too broad; the exam wants the specific discipline.