The critical pressure ratio (p₂/p₁) is given by

A. (p₂/p₁) = [2/(n - 1)] ^{n/(n + 1)}

B. (p₂/p₁) = [2/(n + 1)] ^n/(n-1)

C. (p₂/p₁) = [(n - 1)/2] ^{n + (1/n)}

D. (p₂/p₁) = [(n + 1)/2] ^{n - (1/n)}