Answer: (C) conservation of matter
Solution: Law of conservation of matter or mass states that' total mass of the reactants should always be equal to the total mass of the product that is the total mass is remained conserved in a chemical reaction.
A balanced chemical equation always follow this law.
For example:

Mass of hydrogen = 1 g/mol
Mass of Oxygen = 16 g/mol
Total mass on the reactants = 2(2×1)+(2×16)= 36g/mol
Total mass on the product side = 2[(2×1) +16] = 36 g/mol
As,
Mass on reactant side = Mass on the product side
Therefore, a balanced chemical reaction follows Law of Conservation of mass.
An an increase in
temperature lead to more effective collisions between reactant particles and an
increase in the rate of a chemical reaction because the number of
molecules with sufficient energy to react increases. The answer is number 3.
Answer:
hydrogen + oxygen = water
The last set which is n=4 l=3 m=3 is a valid set