Answer:
A. Polycythemia Vera
Explanation:
Erythrocytosis refers to the increase in a number of the red blood cells by the abnormal cells in the bone marrow.
The increase in the number of the RBC in the blood is a form of cancer caused by the cancerous disease called Polycythemia Vera.
During the polycythemia, the uncontrolled division of RBC leads to the thickening of the blood which disrupts the flow of the blood in the body ( due to the formation of the blood clots in the arteries ad the veins.
Thus, Option-A is the correct answer.
Polycythemia vera is associated with a rapid proliferation of blood cells produced by the bone marrow