If, at a Given Temperature, the Equilibrium Constant for the Reaction

If, at a given temperature, the equilibrium constant for the reaction
H₂(g) + Cl₂(g) ⇌ 2HCl(g) is 5.0, then the equilibrium constant for the reaction
HCl(g) ⇌ (1/2) H₂(g) + (1/2) Cl₂(g) can be represented as

A) 0.040.
B) 25.
C) 0.45.
D) 0.20.
E) 5.0.