The correct answer is Karl Landsteiner. • The blood group system was discovered by Karl Landsteiner. Explanation & Key Takeaways: • Karl Landsteiner • Karl Landsteiner has been credited for the discovery of the ABO blood group system in 1900. • His extensive research on serology led to the identification of major blood groups such as O, A, and B types, compatibility testing, and subsequent transfusion practices. • Friedrich Stromeyer • Prof Friedrich Stromeyer FRS FRSE was a German chemist. • He was the discoverer of cadmium. • Karl Wilhelm Scheele • He was a German Swedish chemist who independently discovered oxygen, chlorine, and manganese. • William Murdock • He was a pioneer in the use of coal gas for lighting and made significant advances in the use of steam power. • He was one of the first people in the world to use coal gas for lighting his home post-dark.