Which of the following attire is most appropriate for a fitness professional during a video-based virtual training session?

Wearing a solid color t-shirt during a video-based virtual training session is the most appropriate choice for a fitness professional for several reasons. It strikes the right balance between being professional and comfortable, which is essential in a fitness setting. A t-shirt allows for ease of movement and demonstrates that the trainer is prepared to engage in physical activity, which can be motivating for clients.

Additionally, solid colors tend to be less distracting on video, allowing the focus to remain on the trainer's guidance and movements rather than on busy patterns or bright costumes that could divert attention. This choice also conveys professionalism without appearing overly formal, which can make virtual interactions more approachable and relatable for clients.

In contrast, other attire options such as yoga pants and sandals, a formal suit, or a brightly colored costume either lack professionalism, don't allow for comfort and movement, or might be too distracting for a virtual setting, making them less suitable for a fitness training environment.