Which of the following features are correct? Choose correct option. a. The synaptic cleft is the space between the presynaptic and postsynaptic neurons. b. Neurotransmitters are released from the presynaptic neuron into the synaptic cleft. c. The binding of neurotransmitters to receptors on the postsynaptic membrane can be excitatory or inhibitory. d. Electrical synapses are more common in humans than chemical synapses.