Total lung capacity is the sum of which volumes?

1. A capacity is a combination of two or more respiratory volumes. 2. There are four volumes in all: tidal, inspiratory reserve, expiratory reserve and residual. 3. Total lung capacity is the sum of all four, so TLC = TV + ERV + IRV + RV. 4. It represents the total air a person holds after a forceful inhalation. 5. The first option leaves out residual volume, which makes it vital capacity rather than total lung capacity. 6. The third and fourth options each drop one of the four volumes, so both fall short of the total. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 22 "The Respiratory System", section 22.3 The Process of Breathing_