Select the correct statements from the following.

(a) The diaphragm separates the abdominal and thoracic cavities.

(b) The larynx helps in production of the sound and so is called sound box.

(c) Air volumes in breathing movements can be estimated by using a sphygmomanometer.

(d) RV is the total volume of air that will remain in the lungs after a normal expiration.

A sphygmomanometer is a device used to measure blood pressure, not air volumes in breathing movements. Air volumes in breathing movements are typically measured using a spirometer.

Residual Volume (RV) is the volume of air that remains in the lungs after maximal expiration, not after a normal expiration. It's the volume of air that cannot be expelled from the lungs even with maximum effort.