The correct option is A Microsomes
The endoplasmic reticulum is a system of membrane-lined channels found in all eukaryotic cells except mature erythrocytes. During cell fractionation and subsequent ultracentrifugation, broken pieces of endoplasmic reticulum appear as microsomes. Microsomes are the fragments of the endoplasmic reticulum that are attached with the ribosomes when obtained by the centrifugation of homogenized cells.