Muscles of iris and ciliary body are "smooth muscles". Smooth muscle cells arise from undifferentiated mesenchymal cells (embryonic mesoderm). These cells differentiate first into mitotically active cells, myoblasts, which contain a few myofilaments. Myoblasts give rise to the cells which will differentiate into mature smooth muscle cells. Iris is derived from neuroectoderm but the muscles of iris is derived from mesoderm. Thus, the correct option is B.