Tidal volume is
a)	Volume of air inspired or expired
b)	Additional volume of air, a person can inspire by a forcible inspiration
c)	Additional volume of air, a person can expire by a forcible expiration
d)	Remaining volume of air in the lungs even after a forcible expiration

(a)

Volume of the air inspired or expired. Pulmonary volume is the volume of air present in the lungs it is divided into four different types according to the volume of air present in the lungs

(i) Tidal Volume (TV) The volume of the air inspired or expired involuntarily in each normal breath. It is about 500 mL of air in average young adult man

(ii) Inspiratory Reserve Volume (IRV) The maximum volume of the air, which a person can inhale over and above tidal volume by deepest, possible voluntary inspiration. It is about 3000 mL

(iii) Expiratory Reserve Volume (ERV) The volume of the air which can be expired over and above the tidal volume with maximum effort. It is about 1100 mL

(iv) Residual Volume (RV) The volume of the air left in the lungs even after the maximum forceful expiration. It is about 1200 mL