What is the formula for the reaction when water acts as an acid, donating H⁺ to NH₃?
a) H₂O + NH₃ → H₄O⁺ + NH₂⁻
b) H₂O + NH₃ → OH⁻ + NH₄⁺
c) H₂O + NH₃ → NH₄⁺ + OH⁻
d) H₂O + NH₃ → H₃O⁺ + NH₂⁻