Additional muscles in the ...... impact the ability of humans to increase the strength of inspiration and expiration. Complete the given $NCERT$ statement with an appropriate option.

State the sequence of events for inspiration (breathing in).
$I$ - Increase in lung volume
$II$ - Decrease in intrapulmonary pressure
$III$ - Contraction of respiratory muscles
$IV$ - Increase in thoracic volume
$V$ - Air rushes into the lungs

Which muscles undergo contraction during normal expiration?

What structures are responsible for the breathing process?

Select the correct statement.

During inspiration,the volume of thoracic cavity increases because of