Statement-I : Mass numbers of most of the elements are fractional.
Because
Statemen-II Mass numbers are obtained by comparing with the mass number of carbon taken as 12.

Options

A. Statement-I is true, Statement-II is true , Statement-II is correct explanation for Statement-I.
B. Statement-I is true, Statement-II is true , Statement-II is NOT a correct explanation for statement-I
C. Statement-I is true, Statement-II is false
D. Statement-I is false, Statement-II is true