What is the percent-yield of H₂ in the reaction below when an equimolar mixture of CH₄ and CO₂ with an initial total pressure of 20.0 atm reaches equilibrium at 1200. K, at which Kp = 3.548 x 10⁶?

CH₄(g) + CO₂(g) ⇋ 2CO(g) + 2H₂(g)

A. 84.5 %
B. 98.0 %
C. 63.4 %
D. 48.9 %
E. 76.7 %