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

A. Axons in muscle cells must both have structures that make in secrete the same molecules
B. Axons in muscle cells must both have receptors that recognize the same small molecules
C. Axons must have structures that make and secrete molecules in muscle cells must have receptors that recognize these molecules.
D. Muscle cells must have structures that make and secrete molecules in the axons must have receptors that recognize these molecules
I think its D