Which One of the Following Statements Is True of Enzyme

Which one of the following statements is true of enzyme catalysts?

A) They bind to substrates but are never covalently attached to substrate or product.
B) They increase the equilibrium constant for a reaction,thus favoring product formation.
C) They increase the stability of the product of a desired reaction by allowing ionizations,resonance,and isomerizations not normally available to substrates.
D) They lower the activation energy for the conversion of substrate to product.
E) To be effective,they must be present at the same concentration as their substrates.