Water reaches an equilibrium state according to the following equation: the concentration of hydrogen ions is (1.0 × 10⁻⁷) mol/L. What is the equilibrium constant?

a) (1.0 × 10⁻⁷)
b) (1.0 × 10⁷)
c) (1.0)
d) (7.0 × 10⁻⁷)