A word equation is a written description of a chemical reaction.
All word equations start with the reactants.
Then, what comes next is the word "react to form."
Finally, the products of the equation are mentioned.
An example is,
Zinc and Hypochondriac acid react to form hydrogen gas and zinc chloride.
A. Adding a catalyst. A catalyst by definition is a compound that speeds up reaction rates.
Grams (g) is much lighter than kilograms (kg)
Answer: Option (a) is the correct answer.
Explanation:
A decomposition reaction is defined as a reaction where a compound dissociates into two or more atoms.
For example, 
Whereas a chemical reaction in which two reactants combine together to result in the formation of a compound is known as a synthesis reaction.
For example,
is a synthesis reaction.
Thus, we can conclude that the statement chemical reaction A, because the reactant is a compound identifies the decomposition reaction and describes a substance is involved.