(i) The glottis is guarded by epiglottis
(ii) The lung alveoli are covered with blood capillaries.
(iii) The wall of trachea is supported by cartilage rings.
(i) The glottis is guarded by epiglottis since this prevents entry of food in wind pipe (trachea). When food enters wind pipe, it chokes it, leading to death of person.
(ii) The lung alveoli are covered with blood vessels as oxygen which we take in dissolves in blood, present in these blood capillaries only, since reaches lungs.
(iii) The wall of trachea is supported by cartilage rings since they prevent air passage from collapsing.