Answer question n

(a) We have been able to eradicate it completely by immunization.

(b) This was believed to be so because it was seen that if a person gets a disease once, the body remembers the infection and fights against it with increased vigour the next time.

(c) The basis of the principle of immunization is that our body develops memory for a particular disease by putting the infection in a small dose into the body so that subsequent exposure will not develop into actual diseases.

(d) Vaccines are available for – Tetanus, diphtheria, whooping cough, measles, polio etc.