Answer:
The product of this reaction is C. magnesium nitride
Step-by-step explanation:
First of all, the chemical formula for this reaction is wrong. It should be :
⇒
(I)
When we have a chemical reaction, for example :
⇒

The substances A and B are called the reactants.
The substance C is called the product.
In a chemical reaction there could be one or more reactants and one or more products.
In the equation (I) the magnesium nitride is in the products side.
Therefore, in the chemical reaction of magnesium and nitrogen the magnesium nitride is the product.
The correct option is C. magnesium nitride