Which of the following cannot be measured by spirometry?

Spirometry measures the volume and flow of air during breathing. It is commonly used to evaluate lung function and diagnose respiratory conditions. Residual volume is the volume of air that remains in the lungs after forcible
expiration. It cannot be directly measured by spirometry since it is neither inhaled nor exhaled. It can be measured by techniques like gas dilution or plethysmography. 

(1) Tidal volume is the amount of air that moves in and out of the lungs during normal breathing. It can be measured
accurately, using spirometry. 

(2) Inspiratory reserve volume is the additional volume of air that can be inhaled forcefully after a normal inhalation. Spirometer records the inspiratory reserve volume when the person takes a deep breath. 

(4) Vital capacity is the maximum volume of air that can be exhaled forcefully after a maximal inhalation. It is the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume. Vital capacity can be measured by using
spirometry by making the person take a deep breath and exhale forcefully.