6. Both water and glucose possess an-OH group that can react with the terminal phosphate of ATP in a reaction facilitated by hexokinase. Despite this similarity, glucose is approximately a million times more reactive as a substrate compared to water. The most plausible explanation for this difference is:
(A)Glucose has more -OH groups per molecule than does water.
(B) The-OH group of water is attached to an inhibitory H atom, while the glucose-OH group is attached to C.
(C) The larger glucose binds better to the enzyme； it induces a conformational change in hexokinase that brings active-site amino acids into position for catalysis.
(D) Water and the second substrate, ATP, compete for the active site resulting in a competitive inhibition of the enzyme.
(E)Water normally will not reach the active site because it is hydrophobic.