If the refractive index of glass is 1.5, what is the critical angle at the air-glass interface?

• A.sin^-1\(\frac{1}{2}\)
• B.sin^-1\(\frac{2}{3}\)
• C.sin^-1\(\frac{3}{4}\)
• D.sin^-1\(\frac{8}{9}\)
• E.