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?
-C₄H₁₀(g) + O₂(g) $\rightarrow$ CO₂(g) + H₂O(g)

A) 2
B) 4
C) 6
D) 8
E) 10