Excretion is best defined as the removal of

  • A. undigested food from the intestine
  • B. excess water only
  • C. dead cells from the skin surface
  • D. metabolic waste products formed in the cells

Explanation

True excretion eliminates substances made by metabolism, such as urea and CO2. Undigested food never entered the cells, so its removal is egestion, a distinction examiners test regularly.

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