The correct option is D The concentration of the un-ionized molecules must be relatively large compared with the ion concentrations
If a reaction has a small value for K, the equilibrium constant, the concentration of the un-ionized molecules must be relatively large compared with the ion concentrations.The equilibrium constant is the ratio of the concentrations of products to the concentrations of reactants. The concentration terms are raised to appropriate stoichiometric coefficients. Low value of equilibrium constant means the product concentrations are lower than the reactant concentrations. Hence, the equilibrium lies more towards left. Due to this, the degree of dissociation is low.