Which of the following is a physiological measure often used in biofeedback?

Blood pressure is a physiological measure that is often used in biofeedback because it reflects the body's response to stress and can be controlled through various relaxation techniques. Biofeedback is a therapeutic approach that enables individuals to gain awareness and control over physiological functions by providing real-time data on specific bodily processes. By using instruments that monitor blood pressure, practitioners can help clients learn how to reduce stress responses and improve overall health by consciously altering their physiological state.

Other options such as social interactions, verbal communication, and cognitive tasks involve psychological and social aspects rather than direct physiological measures. While they may influence physiological responses, they do not represent measurable bodily functions in the way blood pressure does, making them less relevant in the context of biofeedback training and practice.