Which meridian governs the body's defenses and plays a role in respiratory health in acupuncture?

The lung meridian is considered to govern the body's defenses and is directly associated with respiratory health in acupuncture. It plays a fundamental role in the process of respiration and the regulation of Qi (vital energy) within the body. The lungs are responsible for taking in air and distributing oxygen, which is essential for overall vitality and immune function.

In traditional Chinese medicine, the lung meridian is also thought to be intimately connected to the body’s defensive Qi, known as "Wei Qi." This Wei Qi helps to protect against external pathogens such as colds and infections. By strengthening the lung meridian, acupuncturists aim to enhance immune responses and improve respiratory conditions, emphasizing its crucial role in maintaining health.

The other meridians, while important in their respective functions, do not primarily focus on respiratory health or the specific aspect of governing the body's defenses in the same way that the lung meridian does. Therefore, the lung meridian stands out as the correct answer in this context.