Practice question

Correct option is D, 20 cm. In Excretory System, the accurate description is 20 cm, and that is what you should commit to memory. Keep the definition tight and the role clear — 20 cm is the option that correctly names the structure, process, or principle asked for in Excretory System. Then 20 cm is the answer you can defend. Check yourself by covering the options and writing the answer first, then matching the letter — that builds confidence. If the wording feels dense, translate it into everyday language first, then map that plain sentence back onto 20 cm. Remember that physiology questions reward precise language: name the process, the location, and the outcome, then match that to the option text.