Final answer:
A PMA-Certified Teacher's ability to deliver Pilates exercise benefits to a client is directly impacted by their teaching experience, which allows for effective guidance and adaptation to external factors.
Step-by-step explanation:
The factor that directly impacts a PMA-Certified Teacher's ability to deliver Pilates exercise benefits to a client is b) Teaching experience. While equipment quality, ambient temperature, and a client's diet can influence the practice and outcomes, the teacher's experience is fundamental in tailoring sessions to the client's needs, providing proper guidance, and ensuring safe and effective exercise execution. A well-experienced instructor can adapt to various situations, use equipment effectively regardless of its quality, and help clients manage external factors such as diet and environment to maximize the benefits of Pilates.