Answer:
A) Polycythemia Vera
Step-by-step explanation:
Erythrocytosis refers to a condition of the blood in which the count of the Red blood cell in the blood increases due to abnormal proliferation of the red blood cells.
The main cause of the primary erythrocytosis is caused by a disease called polycythemia Vera in which the stem cell starts producing a large number of a red blood cell.
The increased number of the red blood cell leads to the thickening of the blood which lowers the flow of the blood in the body and the formation of blood clots.
Thus, Option-A is the correct answer.