44. Which of the following statements concerning transmission of nerve signals is correct? (A) Signal transmission is slower in myelinated axons than unmyelinated axons. (B) Signal is transmitted along the axon by hyperpolarization of axonal membrane. (C) Many of the receptors of neurotransmitters are ligand-gated ion channels. (D) All neurotransmitters are excitatory when they bind to their receptors.