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

Which of the following reactions will result in a reduced total pressure if run to completion?

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