Which of the following has no central nervous system?
Correct answer: A. Hydra
- A. Hydra
- B. Man
- C. Planaria
- D. Cockroach
Explanation
Hydra has a diffuse nerve net but no central nervous system, brain, or spinal cord. Planaria, cockroach, and humans all possess central concentrations of nervous tissue, so choosing planaria overlooks its cerebral ganglia and longitudinal nerve cords.
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