Questions

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.

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

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.

Orographic precipitation or Rain produced when moist air is lifted as it moves over a mountain range. As the air rises and cools, orographic clouds form and serve as the source of the precipitation, most of which falls upwind of the mountain ridge.

Some also falls a short distance downwind of the ridge and is sometimes called spillover. On the lee side of the mountain range, rainfall is usually low, and the area is said to be in a Rain Shadow. 

The earth's atmosphere is composed of 4 layers. 

1. Troposphere

2. Stratosphere

3. Ionosphere

4. Mesosphere

The ozone layer is located in the lower region of the Stratosphere which extends at 11 - 50 kms from the Earth's suface.