Correct option (d) neurotransmitters are released by the axon endings and not by dendrites
Explanation :
A synapse occurs where the axon of one neuron (the pre-synaptic neuron) meets other the dendrite or the cell body of another (the post-synaptic neuron). At the tip of the pre-synaptic axon is a button shaped swelling called a synaptic knob, inside which are numerous mitochondria and vesicles packed with a substance called a neurotransmitter.
Thus, neurotransmitters at the time of nerve impulse diffuse across the space and bind to receptors in the membrane of the post-synaptic cell. This opens ion channels in the post-synaptic membrane of tire post-synaptic cell resulting in a change in the post-synaptic cell,* membrane potential and (if the cell is sufficiently excited) in the consequent generation of a nerve impulse.
