Answer:
C. Nitrogen gas and hydrogen gas
Step-by-step explanation:
Chemical reactions are composed basically of reagents (usually two or more) and products (which may be one or more).
Reaction example:
A + B ⇒ AB
where A and B are reagents and AB represents a product.
In the reaction of the question we have ammonia as the end product, resulting from the reaction between nitrogen gas and oxygen gas.
Example of ammonia formation reaction:
N₂ (g) + 3H₂ (g) ⇔ 2NH₃ (g)
where (g) represents the physical state of atoms (gas) and the reverse arrows (⇔) represent a reversible reaction within the chemical equilibrium.