When a person puts food in his mouth, then teeth cut it into small pieces, chew and grind it. The glands A in the mouth secrete a substance B which is mixed with the food by the tongue. Substance B contains an enzyme C which starts the digestion of food in the mouth. The slightly digested food from the mouth goes down a tube D. The special type of movements E in the walls of tube D pushes the food into the stomach for further digestion. The stomach wall secretes gastric juice containing three substance F, G and H. One of the functions of F is to kill bacteria which may enter the stomach with food. The substance G protects the inside layer of the stomach from the damaging effect of substance F whereas substance H is an enzyme for digestion. The partially digested food then enters into the small intestine for further digestion. (a) What is (i) gland A (ii) substance B, and (iii) enzyme C? (b) Name the tube D. (c) What is the movement E known as? (d) What are (i) F (ii) G, and (iii) H?