Which Statement Describes the Currently Accepted Theory of How an Enzyme

Which statement describes the currently accepted theory of how an enzyme and its substrate fit together?

A) When the product binds to the enzyme,the substrate changes shape to accommodate the reaction.
B) The enzyme is like a key that fits into the substrate,which is like a lock.
C) The active site is permanently changed by its interaction with the substrate.
D) As the substrate binds to the enzyme,the shape of the active site changes to accommodate the reaction.