In each of the following two questions two statements are given one labelled as the Assertion(A) or Statement I and the other labelled as the reason (R) or statement II. Examine these statements carefully and mark the correct choice as per following instructions
Assertion (A) - The atomic mass of an element is not only relative but is average relative mass of an atom
Reason (R) - The average word is essential because the element, in general, is a mixture of different isotopes and atomic mass is the average of these relative atomic mass.
A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true