1. It is a muscular tube containing semicircular rings of cartilages.   5   7   16   14   Hint Half-n-half Clue   2. Exchange of gases occurs here.   7   3   13   2   Half-n-half Clue   3. Larger dust particles in the inhaled air are trapped in the mucus and hair found here.   5   16   1   8   Half-n-half Clue   4. Food descends from mouth to stomach through this muscular tube.   3   12   9   10   Half-n-half Clue   5. It secretes saliva.   3   9   2   13   Half-n-half Clue   6. These are formed by division of trachea.   14   15   6   16   Half-n-half Clue   7. Bile is stored here.   7   15   10   6   Half-n-half Clue