GTP-binding proteins act as _______________: they are in their active conformation when GTP is bound, but they can hydrolyze this GTP to GDP, which releases a phosphate and flips the protein to an inactive conformation.

The efficiency of coagulation process is not good during the condition of low temperature, because ( ) A: coagulants will not hydrolyze completely B: the hydration of colloidal particles is enhanced, which hinders the coagulation process C: the viscosity of water is high, so the Brownian motion is weak, making it difficult for colloids to aggregate D: The rate of coagulants hydration is too high