# Which of the following mixtures is used by divers in their breathing apparatus for respiration purposes?

$\begin{array}{1 1} Helium \;+Oxygen \\ Neon\;+Oxygen \\ Argon\;+Oxygen \\ Xenon\;+Oxygen \end{array}$

Heliox is a breathing gas composed of a mixture of helium and oxygen, whose range of medical uses has since expanded greatly, mostly because of the low density of the gas
The mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires less effort to breathe in and out of the lungs.