The correct option is D All of the above
Simple epithelial cells can be derived from all the three germinal layers like epidermis, endodermis and mesoderm.The cells in this tissue are very closely packed with very less intercellular spaces and have a free surface on the other side. This tissue may be simple in structure but by structural modifications and shapes of cells in it, it is again classified into 3 major types along with 3 modified types - squamous, cuboidal and columnar simple epithelial cells. In cuboidal simple epithelial cells, they are cuboid in shape and a round nucleus is seen at the centre. It is mostly found in ducts of glands and tubular parts of the nephrons.