question_answer

  Give reasons (a) Rings of cartilage are present in trachea. (b) Lungs always contain a residual volume of air.         

Answer:

                  (a) Rings of cartilage are present in trachea to prevent it from collapsing when less air is present in it.                                                      (1) (b) Lungs always contain a residual volume of air to absorb maximum amount of oxygen and to release carbon dioxide.                            (1)