Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Hydrogen is an environment friendly fuel.
Reason R: Atomic number of hydrogen is 1 and it is a very light element.
In the light of the above statements, choose the correct answer from the options given below

The Assertion states that hydrogen is an environment friendly fuel. This is true because when hydrogen burns, it produces only water as a byproduct:

$$2H_2 + O_2 \rightarrow 2H_2O$$

No harmful gases like CO$$_2$$, SO$$_2$$, or NO$$_x$$ are produced, making it environmentally friendly.

Now, the Reason states that the atomic number of hydrogen is 1 and it is a very light element. This is also true — hydrogen has atomic number 1 and is indeed the lightest element.

However, the reason is not the correct explanation of the assertion. Hydrogen being environment friendly is because its combustion product is water (non-polluting), not because of its atomic number or mass.

Hence, the correct answer is Option B: Both A and R are true but R is NOT the correct explanation of A.