Firstly, I focussed on "If you remove my 1st & 2nd letters, you can't see me". The first thing that comes to mind which we can’t see is the "AIR".

So now, what 4 letter words can be formed ending with "AIR"? Think of all the words from A to Z, considering which one lies above you. That is how we get to "HAIR".

Now, which 5 letter word can be formed ending with "HAIR"? Starting with A to Z, we reach "CHAIR" and also, it lies below us.

And the required answer is "CHAIR".

Grasslands are found in most ecoregions of the Earth.

For example, there are five terrestrial ecoregion classifications of the temperate grasslands, savannas, and shrublands ecosystem, which is one of eight terrestrial ecozones of the Earth's surface.

The given number series is 

3, 5, 8, 15, 28, 51, ?

Here the pattern it follows is

3

3 + 2 = 5 ( add prime number less than 3 i.e, 2)

5 + 3 = 8 (3 is prime number less than 5)

8 + 7 = 15 (7 is prime number less than 8)

15 + 13 = 28 (13 is prime number less than 15)

28 + 23 = 51 (23 is prime number less than 28)

51 + 47 = 98 (47 is prime number less than 51)

Hence, the next number in the given number series is 98.

The day of the week repeats every 7 days.

Given today is Friday. Again Friday is repeated on the 7th day, 14th,... on 7 multiple days.

Hence, Friday is on the 63rd day, as 63 is multiple of 7.

Now, the required day of the week on the 65th day is Sunday.

Bond Order  = 1/2[ Nb - Na]

where

Nb = Number of electrons in bonding molecular orbitals.

Na = Number of Electrons in antibonding molecular orbitals

Bond Order of N2⁺:

Total number of electrons: 13

Electronic Configuration= :σ1s² σ*1s² σ2s² σ*2s² π 2py² [π2pz² σ2px1 ]

Bond Order = [9-4]/2 = 5/2 = 2.5.

Methane is the main component of biogas and natural gas.

The given words are related in a way that, an optimist is a person whose outlook is cheerful. Similarly, a pessimist is a person whose outlook is gloomy.

The answer is not (b) because a pessimist does not have to be mean. Options (c) and (a) are incorrect because neither words describe the outlook of a pessimist.

Hence, Optimist is to cheerful as Pessimist is to Gloomy.

Madhya Pradesh has the highest number of 55770 fully covered tribal habitations with the safe drinking water in the country followed by Odisha and Jharkhand.