Step 1: Set the scene clearly.
Rakesh is the speaker, delivering a presentation verbally. Kunal, the CEO, is the listener and is not speaking at all. He is acknowledging Rakesh only through gestures, body language, and facial expressions.
Step 2: Broadly classify communication types.
Communication is primarily divided into two broad categories: Verbal Communication (which uses spoken or written words) and Non-Verbal Communication (which uses all signals except words).
Step 3: Determine what Kunal is NOT using.
Kunal is not speaking any words (not verbal-oral) and not writing anything down (not verbal-written). This immediately rules out all forms of verbal communication.
Step 4: Identify the specific signals Kunal is using.
The three signals mentioned are: (1) gestures, such as nodding or hand movements; (2) body language, such as posture, sitting forward to show engagement; and (3) facial expressions, such as smiling or making eye contact to show attention and interest.
Step 5: Map these signals to the correct communication type.
Gestures, body language, and facial expressions are all classic examples of non-verbal communication, often studied under the field of kinesics (the study of body movement as communication).
Step 6: State the conclusion.
Since Kunal is communicating his attention and acknowledgment entirely through physical signals without uttering a single word, he is unambiguously using non-verbal communication.
\[ \boxed{ \text{Non-verbal communication} } \]