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

Active listening represents a form of non-verbal communication because it involves interpreting the unspoken cues from a speaker, such as body language, facial expressions, and even tone of voice, while demonstrating attentiveness and understanding. Despite the term "active listening" implying engagement through hearing, it heavily relies on the non-verbal aspects that accompany spoken words, making it a critical skill in effective communication.

The other options focus primarily on verbal or written forms of communication: written memos and email correspondence are both textual forms, conveying messages through written language rather than through non-verbal signals. Giving a public speech, while it may incorporate some non-verbal elements (like gestures), fundamentally is a verbal communication activity, as the primary conveyance of information derives from spoken language.