Which of the following must be true about the structures of axons and muscle cells in order for nerve impulses to stimulate muscle contraction?

Question

a- Axons and muscle cells must both have structures that make and secrete the same small molecules.
b- axons and muscle cells must both have receptors that recognize the same small molecules.
c- Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules.
d-Muscle cells must have structures that make and secrete molecules, and axons must have receptors that recognize these molecules.