Identify the gases used to fill in electric bulbs.

Given below are two statements:
Statement-$I$: Noble gases have very high boiling points.
Statement-$II$: Noble gases are monoatomic gases. They are held together by strong dispersion forces. Because of this,they are liquefied at very low temperatures. Hence,they have very high boiling points.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following statements is $NOT$ correct regarding $Helium$?

Least chemical activity is shown by

What is the trend in the atomic radii of noble gases as we move down the group?

$XeF_4$ reacting strongly with water gives .......