Given below are two statements :
Question:

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Hydrogen is the most abundant element in the Universe, but it is not the most abundant gas in the troposphere.

Reason $R$ : Hydrogen is the lightest element.

In the light of the above statements, choose the correct answer from the given below

1. $\mathrm{A}$ is false but $\mathrm{R}$ is true

2. Both $\mathrm{A}$ and $\mathrm{R}$ are true and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$

3. $\mathrm{A}$ is true but $\mathrm{R}$ is false

4. Both $\mathrm{A}$ and $\mathrm{R}$ are true but $\mathrm{R}$ is NOT the correct explanation of $\mathrm{A}$

Correct Option: , 2

Solution:

Hydrogen is most abundant element in universe because all luminous body of universe i.e. stars \& nebulae are made up of hydrogen which acts as nuclear fuel \& fusion reaction is responsible for their light.