Which scenario represents a common etiquette mistake?

Interrupting a conversation is a common etiquette mistake because it disrupts the flow of communication and can lead to feelings of disrespect or disregard for the other person's thoughts. Effective communication relies on listening as well as speaking, and when someone interrupts, it prevents a complete exchange of ideas and can make the interrupted party feel that their input is not valued. In social and professional settings, it is important to wait for an appropriate moment to contribute, demonstrating respect for others and allowing for a more constructive dialogue.

The other scenarios presented—offering a warm greeting, politely waiting for your turn, and addressing someone properly—are all examples of good etiquette. These actions promote a positive interaction and show consideration for others, helping to foster a respectful and friendly environment.