The equilibrium constant, Kp , for the reaction

CO(g) + H2O(g) CO2(g) + H2(g)

at 986°C is 0.63. A rigid cylinder at that temperature contains 1.2 atm of carbon monoxide, 0.20 atm of water vapor, 0.30 atm of carbon dioxide, and 0.27 atm of hydrogen. Is the system at equilibrium?

A. Yes.
B. The starting concentrations of all substances must be known before deciding.
C. No, the forward reaction must proceed to establish equilibrium.
D. The volume of the container must be known before deciding.
E. No, the reverse reaction must proceed to establish equilibrium.