Leukaemia is a cancer of the:

blood

The correct answer is Option (4) -blood

Leukemia is a cancer of the blood.

Leukemia affects the blood-forming tissues in the body, primarily the bone marrow and the lymphatic system. In leukemia, there is an abnormal proliferation of white blood cells, which are responsible for fighting infections. This uncontrolled growth of white blood cells disrupts the normal production of other blood cells, such as red blood cells and platelets.

As a result, individuals with leukemia may experience symptoms such as fatigue, weakness, frequent infections, easy bruising or bleeding, and swollen lymph nodes. Leukemia can be classified into different types based on the type of white blood cells affected and the rate of disease progression.

Treatment for leukemia typically involves chemotherapy, radiation therapy, targeted therapy, or stem cell transplantation, depending on the specific type and stage of the disease.