Final answer:
COPD can be located in the Alpha Index under the Respiratory system since it involves progressive lung diseases affecting breathing and airflow.
Step-by-step explanation:
COPD, or Chronic Obstructive Pulmonary Disease, can be found in the Alpha Index under the category of the Respiratory system. This is because COPD is a group of progressive lung diseases that cause airflow blockage and breathing-related problems, affecting the lungs and respiratory tract. The most common conditions falling under COPD are emphysema and chronic bronchitis. COPD does not relate directly to the digestive, cardiovascular, or nervous systems, which are concerned with digestion, circulation and heart function, and brain and nerve function, respectively.