The reaction of $P_2$ with $X$ leads selectively to $\mathrm{P}_4 \mathrm{O}_6$. The $\mathrm{X}$ is
The reaction of $P_2$ with $X$ leads selectively to $\mathrm{P}_4 \mathrm{O}_6$. The $\mathrm{X}$ is
dry $\mathrm{O}_2$
a mixture of $\mathrm{O}_2$ and $\mathrm{N}_2$
moist $\mathrm{O}_2$
$\mathrm{O}_2$ in the presence of aq. $\mathrm{NaOH}$
Solution
White phosphorus on reaction with limited supply of oxygen gives lower oxide $P_4 \mathrm{O}_6$. Therefore, air $\left(\mathrm{O}_2+\mathrm{N}_2\right)$ is a good source for controlled supply of oxygen and the best choice for controlled oxidation of white phosphorus into lower oxide $\mathrm{P}_4 \mathrm{O}_6$.