(i) The glottis is guarded by epiglottis because it prevents the entry of food in wind pipe. If the food enters wind pipe, then it chokes it, leading to the death of the person.

(ii) The lung alveoli are covered with blood vessels because the oxygen that we inhale dissolves in the blood, present in these blood capillaries only, as it reaches the lungs.

(iii) The wall of trachea is supported by cartilage rings because these rings prevent the air passage from collapsing.
2 3 2