1. The surface of the crown of the tooth is covered with a strong protective layer known as the _______.   root   enamel   dentine   cavity   Hint Half-n-half Clue   2. The mucus in the stomach protects the stomach tissues from the action of enzymes.   True   False   3. The part of the tooth outside the socket of the jaw is known as the crown.   True   False   4. Which of the following prevents food from entering the trachea (wind pipe)?   pharynx   larynx   glottis   epiglottis   Half-n-half Clue   5. How many teeth does an adult human being normally have?   16   20   30   32   Half-n-half Clue   6. Which of the following is the common passage for the food eaten and the air breathed?   esophagus   pharynx   trachea   larynx   Half-n-half Clue   7. The stomach is lined with mucous membrane.   True   False