In contrast to inhalation, exhalation: Select one: a. is an active process caused by decreased intrathoracic pressure. b. occurs when the diaphragm lowers and expels air from the lungs. c. is a passive process caused by increased intrathoracic pressure. d. requires muscular effort to effectively expel air from the lungs.

C. is a passive process caused by increased intrathoracic pressure.

Explanation:

Inhalation is an active process as it includes the contraction of muscles and diaphragm. Exhalation is a passive stage of breathing. It does not include any muscular contraction. Rather, diaphragm and the external intercostal muscles become relaxed. This reduces the volume of the thoracic cavity and lungs. The reduced volume causes increased air pressure in alveoli as compared to the atmospheric pressure. The increased pulmonary pressure drives the movement of air towards the outside of the body.