An organism appears to be a segmented worm. Upon observation, it is determined that the organism has a closed circulation, a mouth, and an anus and does not have an exoskeleton. The organism most likely belongs to the phylum:

Explanation

Annelida: This phylum includes segmented animals like; earthworms, leech, etc Their body is soft and bilaterally symmetrical Their body is divided into the ring like grove(segments) called annuli. They have a complete digestive system from the mouth to anus Excretion is by nephridia. They have a closed circulatory system. Sexes may be separate or united (sexual reproduction ). The true body cavity is present. Eg; Pheretima, leech.