1. Which of the following structures is responsible for the exchange of gases in the lungs? A. Alveoli B. Bronchi C. Trachea D. Diaphragm Answer: A. Alveoli Rationale: Alveoli are the tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide occurs, which is essential for respiration. 2. The movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration is known as: A. Osmosis B. Diffusion C. Filtration D. Active transport Answer: A. Osmosis Rationale: Osmosis is the process by which water moves through a semipermeable membrane, balancing solute concentrations on both sides of the membrane. 3. Which hormone regulates calcium levels in the blood? A. Insulin B. Thyroxine C. Parathyroid hormone D. Cortisol Answer: C. Parathyroid hormone Rationale: The parathyroid hormone is secreted by the parathyroid glands and plays a critical role in regulating serum calcium levels. 4. During the cardiac cycle, the period of ventricular relaxation is called: A. Systole B. Diastole C. Isometric relaxation D. Ventricular ejection Answer: B. Diastole