Correct Answer: D
Explanation:
Sol. Karl Landsteiner was an Austrian biologist and physician. He is noted for having first distinguished the main blood groups in 1900, having developed the modern system of classification of blood groups from his identification of the presence of agglutinins in the blood and having identified with Alexander S. Wiener, the Rhesus Factor in 1937, thus enabling physicians to transfuse blood without endangering the patient’s life.