Answer : The correct option is, (A) by counting up each individual atom and make sure the atom numbers are the same in the reactants and the products
Explanation :
According to the law of conservation of mass, the mass remains conserved that means the total number of atoms present on the reactant side should always be equal to the number of atoms present on the product side.
The given unbalanced reaction is,

The number of atoms of hydrogen are 2 on reactant side and 3 atoms of hydrogen on product side. Thus equation is not balanced.
The balanced reaction will be,

Hence, the correct option is, (A)