Hiccup occurs due to

Name the important parts involved in creating a pressure gradient between the lungs and the atmosphere during normal respiration.

State whether the given statements are true or false.
$I.$ Ventilation in humans is an active process.
$II.$ Diaphragm helps in generating the pressure gradient in the lungs.
Choose the correct option.

Explain the mechanism of expiration.

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

$A$: Normal expiration during quiet breathing,unlike inspiration,is a passive process because no muscular contractions are involved.
$R$: Normal expiration results from the elastic recoil of the chest wall and lungs.