Which of the following statements about signal deactivation is false?

A. Hormone response systems respond to very small changes in hormone concentration.

B. Second messengers are short-lived because cytoplasmic enzymes convert them to their inactive forms.

C. When G proteins hydrolyze GTP to GDP, they become inactive and halt production of second messengers

D. Phosphatases terminate phosphorylation cascades by adding phosphate groups to proteins in the phosphorylation cascade.