Dendrites are the small extension of nerve cells that receives signals from sensory receptors or other neurons. The nerve impulse is not conducted by them which makes options C and D incorrect. The long extension of cell body of nerve cell is called as axon that serves to conduct the nerve impulse away from the cell body. The increased diameter of axon results in reduced resistance to local current flow which in turn causes the action potential at its one site to activate the adjacent site. This makes option B correct. Soma is the metabolic center of the nerve cell where the metabolic contents are manufactured. It is not involved in nerve impulse conduction. This makes option A incorrect. Correct answer is B.