When the Following Equations Are Balanced Using the Smallest Possible $\rightarrow$

When the following equations are balanced using the smallest possible integers, what is the number in front of the underlined substance in each case?
-N₂(g) + O₂(g) $\rightarrow$ N₂O₃

A) 1
B) 2
C) 3
D) 4
E) 6