Which of the following gases is quite insignificant for the regulation of respiration rhythm?

How will a man's respiration be affected if he ascends to a height of $25000$ feet?

Select the correct statement regarding the respiratory rhythm centers.

Where are the respiratory centers located in the brain?

Select the correct statements regarding Hering-Breuer reflex.
$i$. Stretch receptors of the lungs are stimulated during maximum forceful expiration.
$ii$. Vagus nerves send impulses to the expiratory center.
$iii$. Prevents lungs from inflation to the point of bursting.
$iv$. Controls depth and rhythm of respiration.
$v$. Promotes the lungs for maximum inflation.
Choose the correct option:

When $CO_2$ concentration in blood increases,breathing becomes