Contraction of the diaphragm decreases the volume of the thoracic cavity.

a. True

b. False

FALSE

Explanation:

The diaphragm is a dome-shaped muscular organ and makes the floor of the thoracic cavity. Contraction of diaphragm lowers down its dome and makes it a flat structure which in turn increases the volume of the thoracic cavity. It occurs during inhalation.

The increased volume of thoracic cavity facilitates the expansion of lungs and reduction in air pressure within alveoli to allow the atmospheric air to flow from outside the body into alveoli via the respiratory tract.