Which of the Following Reactions Will Result in a Reduced $\rightarrow$

Which of the following reactions will result in a reduced total pressure?

A) CH₄(g) + 2O₂(g) $\rightarrow$ CO₂(g) + 2H₂O(g)
B) 2N₂O(g) $\rightarrow$ 2N₂(g) + O₂(g)
C) 2HI(g) $\rightarrow$ H₂(g) + I₂(g)
D) 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O( )