<prompt> By spirometry, one can measure -Residual volumeFRCTLCTidal volume  <response>: Ans. is d i.e., Tidal volume o Pulmonary ventilation can be studied by recording the volume movement of air into and out of the lungs, a method called spirometry.o A spirometer is a device in which, one breathes into and out of the device.o The volume of air breathed in or out are measured.o Spirometry can measure spirometric measurement are : - Tidal volume TV, inspiratory reserve volume IRV, expiratory reserve volume ERV, and vital capacity VCr FEV1.o As residual air residual volme can not be expired residual volume is the amount of air remaining in the lung after maximum possible expiration, residual volume cannot be measured by spirometry ,o Therefore, the capacities which have residual volume as one of their components, cannot be measured by spirometry.o These capacities are functional residual capacity ERV RV and total lung capacity VC RC.o The commonly employed methods for functional residual capacity FRC estimation are: -i Gas-dilution methods : - Helium dilution technique, nitrogen washout technique.ii Plethysmography 