A

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Q. Which among the given statements is right?

  • (A) flat worms are with parenchymal circulation
  • (B) sponges have canal system and they need a continuous current of water flow
  • (C) nematodes have parenchymal circulation
  • (D) echinoderms have pseudocoelomic circulation

Explanation by: Admin

Flatworms (Platyhelminthes) do not have a circulatory system. Instead, they rely on parenchymal circulation, where nutrients and gases diffuse through the parenchyma (a type of tissue that fills their body).

  • Sponges (Porifera) have a canal system for water circulation, making option (B) also correct, depending on the context.
  • Nematodes (Roundworms) have a pseudocoelomic fluid that helps in circulation, but they do not rely on parenchymal circulation.
  • Echinoderms (like starfish) have a water vascular system, not pseudocoelomic circulation.

So, A is the best answer, though B is also a factually correct statement.

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