The Balanced Equation for the Solubility Equilibrium of Ba(OH)₂ Is

The balanced equation for the solubility equilibrium of Ba(OH) ₂ is shown below.What is the equilibrium constant expression for the K_sp of Ba(OH) ₂? Ba(OH) ₂(s) ⇌ Ba²⁺(aq) + 2 OH^-(aq)

A) K_sp = {[Ba²⁺][OH^-]²}/{[Ba(OH) ₂][H₂O]}
B) K_sp = {[Ba²⁺][OH^-]²}/[Ba(OH) ₂]
C) K_sp = [Ba²⁺][OH^-]²
D) K_sp = 1/{[Ba²⁺][OH^-]²}