Correct Answer: p - 3, q - 4, r - 1, s - 2

Solution : The correct option is p - 3, q - 4, r - 1, s - 2

In the late 18th century, Edward Jenner developed vaccination. He is credited with creating the smallpox vaccine, which was a turning point in immunisation and disease prevention. In 1953, James Watson and Francis Crick discovered the double helix structure of DNA while working together. Their groundbreaking findings revealed the basic structure of genetic material. With his pioneering research into the categorization of blood types, Karl Landsteiner developed blood grouping in the early twentieth century. His work helped to provide the groundwork for contemporary blood transfusion practises. In 1928, Alexander Fleming developed penicillin. His unintentional discovery of the antibiotic penicillin transformed medicine by introducing the first widely used antibiotic, greatly enhancing the treatment of bacterial diseases.