(a) Blood group:
On the basis of the presence of antigens and antibodies, Karl Landsteiner had divided the human blood into four groups -A, B, AB, and O.
Human blood groups:

Importance of blood group: Due to the knowledge of blood group blood donation has been proved as a boon for the society. By this if the blood is required for the accidental victims and sick persons then blood of appropriate group could be made available by the blood banks or registered voluntary blood donors easily. They are important in the field of law and justice. By taking samples and tests of DNA, culprits could be caught. Deficiency of blood in the body is fulfilled by blood donation and given that blood to person who has deficiency.
(b) Blood Bank:
As far as possible blood should be taken from relatives but if it is not possible then blood could be receive from blood bank opened by government. In government, hospital of every district or private blood bank run by social service institution. To preserve blood in the blood bank, sodium citrate is mixed. It can be preserved for 30 days in blood banks.