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

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

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