During inhalation, which of the following muscle contractions takes place to enlarge the chest cavity from top to bottom? a. Diaphragm moves down.  b. External intercostal muscles move down.  c....

During inhalation, which of the following muscle contractions takes place to enlarge the chest cavity from top to bottom?

a. Diaphragm moves down.

 b. External intercostal muscles move down.

 c. Diaphragm moves up.

 d. Internal intercostal muscles move up.