$A$ healthy human breathes $........$ times per minute.

$I.$ Intra-pulmonary pressure remains less than the atmospheric pressure.
$II.$ There is negative pressure in the lungs compared to the atmospheric pressure.
In which of the above two situations does inspiration take place? Choose the correct option.

During inspiration,the diaphragm:

Explain the mechanism of breathing.

Hiccups can be best described as

Arrange the given steps by which the lungs show inspiration,in the sequence of events occurring first:
$I.$ Increase in the volume of the thoracic chamber in the dorsoventral axis
$II.$ Upward and outward movement of the ribs
$III.$ Contraction of intercostal muscles
$IV.$ Entry of air inside the lungs
$V.$ Contraction of the diaphragm
$VI.$ Increase in the volume of the thoracic chamber in the anteroposterior axis
Choose the correct option.