The first antibiotic discovered by Alexander Fleming in 1928 was:

(A) Penicillin

Alexander Fleming's discovery of penicillin revolutionized medicine by introducing the first widely used antibiotic, which proved effective against a variety of bacterial infections.

(D) Jonas Salk

The polio vaccine was developed by Dr. Jonas Salk. He and his team conducted extensive research in the 1950s, leading to the development of the inactivated polio vaccine (IPV), which became widely used for the prevention of polio. The vaccine was a significant breakthrough in medical science and played a crucial role in the global effort to eradicate polio.