What Is the Concentration of OH^- in a 1

What is the concentration of OH^- in a 1.0 × 10^{-3 M} Ba(OH) ₂ solution?

A) 0.50 × 10^{-3 M}
B) 1.0 × 10^{-3 M}
C) 2.0 × 10^{-3 M}
D) 1.0 × 10^{-2 M}
E) 3.3 × 10^{-4 M}