Which of the following is a characteristic of non-verbal communication?

Non-verbal communication encompasses the ways in which individuals communicate without the use of spoken or written words. Body language, as the correct answer indicates, includes a variety of non-verbal cues such as gestures, facial expressions, posture, and eye contact, which can convey feelings and messages without the need for verbal communication.

In contrast, writing a letter and drafting an email involve the use of written words, which are forms of verbal communication. Speaking clearly also falls into verbal communication, as it relies on the clarity and understanding of spoken language. Therefore, body language stands out as the main characteristic of non-verbal communication, as it relies on physical expressions to convey meaning and emotions.