Which of the following is a common sign of respiratory distress in adults?

Dyspnea during exertion is a common sign of respiratory distress in adults because it reflects the body's struggle to oxygenate itself adequately during physical activity. When an individual experiences dyspnea, or difficulty breathing, especially during exertion, it indicates that the respiratory system is under stress. This could arise from various conditions such as asthma, chronic obstructive pulmonary disease (COPD), pneumonia, or heart conditions that impair airflow or gas exchange.

In contrast, resting comfortably suggests that the individual is not experiencing any distress, which is not indicative of respiratory distress. Auscultation of clear lung sounds typically suggests that there are no obstructions or fluid in the lungs, which does not accompany respiratory distress. Bradycardia, a slower than normal heart rate, can occur in various medical conditions but is not a direct sign of respiratory distress. It does not reflect the respiratory effort or effectiveness in terms of oxygenation.