Question

Which of the following body systems do both roundworms and flatworms lack?

A.circulatory
B.digestive
C.nervous
D.none of the above

Answer 1

I think the answer may be D. But don’t answer yet, I may be wrong.

Answer 2

the correct answer is option A.

Step-by-step explanation:

Roundworms and flatworms cells are close to the animal's outer surface which help them absorbtion. Both roundworm and flatworm use diffusion to respire and for circulation of substances around their body.

They lack circular muscles so only way to undulate is from side to side. They does not need to circulate oxygen they simply diffuse it from skin.

Thus, the correct answer is option A.