Which of the following elements among $He, Ar, Kr,$ and $Xe$ forms compounds in the least amount?

Which of the following does not exist?

The noble gas element that forms the largest number of compounds is .......

At $143 \ K$,the reaction of $XeF_4$ with $O_2F_2$ produces a xenon compound $Y$. The total number of lone pair$(s)$ of electrons present on the whole molecule of $Y$ is . . . . .

Which of the following pairs of inert gases is used in flash bulbs?

Identify the gases used to fill in electric bulbs.