The hereditary disease in which clotting of blood does not take place is known as

The correct option is A Haemophilia

A. Hamophilia is a sex linked recessive disease in which a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected and blood doesn't clot properly. This leads to excessive bleeding.

B. Anaemia is a disease in which there is deficiency of red blood cells or haemoglobin in the blood, resulting in pallor.

C. Leukaemia is a cancer of the body's blood forming tissues including the bone marrow and lymphatic system. It generally involves white blood cells.

D. Xerophthalmia is a eye disease in which there is dryness of the conjunctiva and cornea of the eye caused by vitamin A deficiency.

So, the correct option is 'Haemophilia'.