The correct answer is option D, Round worm
Roundworm belongs to the phylum Nematodes and some common characteristics of Nematodes are – they are small, slender , un-segmented, smooth and shiny. Roundworm has a round body just like a spiny –headed worm which do not have segments . Also they possess a body cavity known as pseudocoel in which the internal body organs lie and the body cavity is not lined with mesodermal cells.
