JEE Main 2018 Chemistry question

At a certain temperature in a 5L vessel, 2 moles of carbon monoxide and 3 moles of chlorine were allowed to reach equilibrium according to the reaction, CO + Cl ⇌ COCl. At equilibrium, if one mole of CO is present then equilibrium constant () for the reaction is -

• (A)2.5Correct
• (B)4
• (C)2
• (D)3