The correct option is D Axon
A Nissl body is a large granular body found in neurons. These granules are rough endoplasmic reticulum (RER) with rosettes of free ribosomes and are the site of protein synthesis. An axon is the tubular process of the nerve cell, that carries impulses away from the cell body. It arises from the cyton at the axon hillock. It has only neurofibrils. Here, Nissl granules are absent.
Thus the correct answer is option A.