Final answer:
The correct answer to the question of what the amount of air taken in one normal breath is known as, is 'tidal volume'.
Step-by-step explanation:
The amount of air taken in one normal breath is known as the tidal volume. Tidal volume (TV) refers to the amount of air that enters the lungs during quiet breathing, typically around 500 milliliters. This is in contrast to the inspiratory reserve volume (IRV), which is the amount of air that can be inhaled beyond a normal breath, and the expiratory reserve volume (ERV), which is the additional air that can be exhaled forcibly after a normal exhalation. Residual volume (RV) is the air left in the lungs after a maximal exhalation, and it ensures that the alveoli do not collapse. In this context, option D, tidal volume, is the correct answer.