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
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.