- A flatworms such as Planaria
- B human beings like us
- C birds and their kin
- D various common insects
Correct answer: A. flatworms such as Planaria
Explanation: Flame cells (protonephridia) carry out excretion in flatworms.
Concept context
Nitrogenous waste, kidney structure, urine formation in the nephron, and hormonal regulation of excretion.
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