Questions

The seven elements — helium, neon, argon, krypton, xenon, radon, and oganesson of Group 18 of the periodic table are Noble or Inert gases.

Radon is the heaviest and Helium is the lightest gases of the noble gases.

In Indian History, Dandi March or Salt Sathyagraha or The Salt March, also known as the Dandi Satyagraha, was an act of nonviolent civil disobedience in colonial India led by Mohandas Karamchand Gandhi to produce salt from the seawater. 

It is also called as 'White Flowing River'.

First nationalisation of commercial banks in India took place in 1969 and second time in 1980.

Envelope is a letter holder for one letter and in the question it mean that it holds one letter. Eye is also a word which starts and end with E but has one letter in the middle.