Hint:The term Synapse is used for the area of the junction of two neurons. There may be electrical synapses or chemical synapses. These areas have message transferring systems in the form of special molecules.
Complete answer: Chemical synapses were discovered by Emil du Bois-Reymond in 1877 and were named in 1906 by Charles Sherrington. He derived the word “synapse” from the Greek terms “syn-” which means together and “haptein” which means to clasp.
Synapses can be classified on the basis of the type of cellular structures serving as the pre-and postsynaptic components. A vast majority of synapses in the mammalian nervous system are classical axodendritic synapses (axon synapsing upon a dendrite) and a variety of other arrangements exist. These other arrangements include but are not limited to axo-axonic, dendro-dendritic, axo-secretory, somatodendritic, dendro-somatic, and somato-somatic synapses.
An axon can synapse onto a dendrite, onto a cell body, or onto another axon or axon terminal, as well as into the bloodstream or into the adjacent nervous tissue.
So, the answer is option A.
Note: In the nervous system, a synapse is a structure that facilitates a neuron or a nerve cell to pass an electrical or chemical signal to another neuron or to the target effector cell.
Synapses are essential for neuronal function. They are the site of neural transmission. Synapses Neurotransmitters are used for this transmission. Acetylcholine is one such neurotransmitter. The neurons are cells that are specialized to pass signals to individual target cells and synapses are the facilitators by which they do so. At the site of a synapse, the plasma membrane of the signal – transferring neuron (also known as the presynaptic neuron) comes into close proximity with the membrane of the target neuron (also known as the postsynaptic neuron).