Which noble gas element from the following exhibits the highest number of different oxidation states?

Which statement about noble gases is not correct?

Least chemical activity is shown by

What is the percentage of $Argon$ in the air (in $\%$)?

Liquid $X$ is used in a bubble chamber to detect neutral mesons and gamma photons. Then,$X$ is

Assertion $(A)$: Noble gases have very low boiling points.
Reason $(R)$: All noble gases have general electronic configuration of $ns^2 np^6$ (except $He$).