What happens during expiration?

Exhalation is the process of expulsion of air through the respiratory tract. Which of the following figures illustrates the process of exhalation?

Assertion : Inspiration occurs due to muscular relaxation.
Reason : During inspiration,the diaphragm and external intercostal muscle contract simultaneously.

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

Sugar is converted into starch when the $pH$ of guard cells increases,which is associated with:

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.