The correct option is A Sodium
Second messengers are intracellular signalling molecules, released by the cell to trigger physiological changes, such as proliferation, differentiation, migration, survival, and apoptosis. Secondary messengers are one of the initiating components of intracellular signal transduction. Examples of second messenger molecules include cyclic AMP, cyclic GMP, inositol triphosphate, diacylglycerol, and calcium.