a. becomes equal to the external environmental air pressure by the action of the respiratory muscles
b. is less than the atmospheric pressure during inspiration
c. is less than atmospheric pressure during inhalation
d. increases when the diaphragm and external intercostal muscles contract
e. is the difference between the pressure in the pleural cavity and that within the lung alveoli.
It seems to me that both a and d are incorrect. A-the respiratory muscles instead act to create differences between the intrathoracic ...
Answers a question about intrathoracic pressure and gives reasoning.