Answer: Option (B) is the correct answer.
Step-by-step explanation:
A chemical reaction that contains same number of atoms on both reactant and product side is known as a balanced chemical equation.
For example,

Number of atoms on reactant side are as follows.
Mg = 1
O = 2
H = 3
Cl = 1
Number of atoms on product side are as follows.
Mg = 1
O = 1
H = 2
Cl = 2
Therefore, to balance this chemical equation we multiply HCl by 2 on reactant side and multiply
by 2 on product side.
Hence, we can conclude that the balanced chemical equation will be as follows.
