Provide your answer to the scenario described below:
 
A child is doing deep breathing exercises as part of morning yoga. He inhales slowly, holds his breath for a few seconds, and then exhales fully.

He notices that his chest and abdomen expand while breathing deeply. His instructor explains that these exercises help improve lung capacity and make breathing more efficient.
 
a. Which process is primarily increased by deep breathing exercises?
 
b. Which structure allows oxygen to pass from the lungs into the blood?
 
 
c. Which muscle helps in expanding the lungs during deep breathing?