Answer
EXCRETION is the process by which the METABOLIC WASTE PRODUCTS formed in the body — chiefly nitrogenous wastes such as urea, uric acid and ammonia, together with excess water and salts — are removed from the body.
The words that earn the mark are METABOLIC WASTE — substances PRODUCED BY THE BODY’S OWN CHEMICAL REACTIONS.
THE DISTINCTION EXAMINERS TEST: excretion is NOT the same as egestion. FAECES are not excretory matter — they are undigested food that never entered the body’s cells and took no part in metabolism. Removing them is EGESTION.
The excretory organs and what each removes: KIDNEYS — urea, excess water and salts, as urine LUNGS — carbon dioxide and water vapour SKIN — water, salts and a little urea, as sweat LIVER — bile pigments from the breakdown of haemoglobin