Which of the following is an example of non-verbal communication?

Non-verbal communication encompasses all forms of communication that do not involve verbal language. Maintaining eye contact is a vital aspect of non-verbal communication as it conveys attentiveness, confidence, and engagement in a conversation. It can express emotions and intentions without the need for words, helping to strengthen the message being communicated.

The other options involve forms of communication that rely on spoken or written words. For instance, writing an email and making a phone call both use verbal content to convey messages, while giving a presentation typically involves both verbal communication (what is being said) and visual aids (like slides), but it still fundamentally relies on spoken language. Thus, maintaining eye contact stands out as a distinct form of non-verbal communication that is crucial for effective interpersonal interactions.