Answer:
C. a long, slender, round body.
Explanation:
The characteristic that can be associated with segmented worms as well as roundworms are; C. a long, slender, round body.
Roundworms and segmented worms are worms with almost the same features, however there are differences, there is complete circulatory system as far as Segmented worms is concerned, whereas roundworms dont have complete one.
In Roundworms there is no heart whereas there is heart in segment worm, but the similarities that be associated with them is in their physical structure, they both have long, slender, round body.
Therefore, option C is correct.