What is the shape of the diaphragm during expiration?

An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure,which forces the air from outside to move into the lungs. This process is known as:

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

The lungs do not collapse during breathing and some air always remains in the lungs which can never be expelled because:

Hiccups are caused by the activity of which of the following?

Guard cell movement furnishes an example of