Answer:
A. 3Mg + N₂ → Mg₃N₂
Step-by-step explanation:
This is a multiple choice question, so the correct answer is in one of the options.
A. is correct. It has three atoms of Mg and two of N on each side of the equation.
B. is wrong. It has four atoms of N on the left and two on the right.
C. is wrong. It has six atoms of Mg on the left and nine on the right.
D. is wrong. It has one atom of Mg on the left and three on the right.