Carbogen is a mixture of

$\begin{array}{1 1}(a)\;O_2\;and\;CO&(b)\;CO_2+O_2\\(c)\;CO_2+O_3&(d)\;O_3+CO\end{array}$

Carbogen is a mixture of $CO_2+O_2$
Carbogen, also called Meduna's Mixture after its inventor Ladislas Meduna, is a mixture of carbon dioxide and oxygen gas.
Hence (b) is the correct answer.
edited Nov 11