2 HI (g) ⇌ H₂ (g) + I₂ (g) at equilibrium, the partial pressure of HI is 1.9 atm and the partial pressures of H₂ and I₂ are 7.9 and 2.3, respectively. What is Kp for this equilibrium?
(a) 0.25
(b) 0.50
(c) 0.75
(d) 1.00