Amplification of a chemical signal occurs when... A. a receptor in the plasma membrane activates several G-protein molecules while a signal molecule is bound to it. B. a cAMP molecule activates one...

A. a receptor in the plasma membrane activates several G-protein molecules while a signal molecule is bound to it.

B. a cAMP molecule activates one protein kinase molecule before being converted to AMP.

C. phosphorylase and phosphatase activities are balanced.

D. receptor tyrosine kinases dimerize upon ligand binding.

I need to know the justification for the correct answer and the falsification of the wrong ones!