Which Expression Defines the Autoionization Constant for Water, K_w

Multiple Choice

Which expression defines the autoionization constant for water, K_w?

A) [H₃O^][OH^]
B) [H₂O][H₃O^]
C) [OH^][H₂O]
D) [H₄O^2][O^2]
E) [H₂O][H₂O]