The correct answer to the question is option 2: Sir Alexander Fleming. Fleming discovered the antibiotic-producing fungus from the Penicillium genus.

Option 1: Louis Pasteur is not the correct answer. While Pasteur made significant contributions to the field of microbiology, he did not specifically discover the antibiotic-producing fungus from the Penicillium genus.

Option 3: Stanley Prusiner is not the correct answer. Prusiner is known for his work on prions and won the Nobel Prize in Physiology or Medicine for his discovery of prions. This is not directly related to the discovery of the antibiotic-producing fungus.

Option 4: Robert Hooke is not the correct answer. While Hooke made important contributions to many fields, including biology and microscopy, he did not specifically discover the antibiotic-producing fungus from the Penicillium genus.

It is important to note that the discovery of the antibiotic-producing fungus is credited to Sir Alexander Fleming. However, it is also worth mentioning that other scientists, including Ernst Chain and Howard Florey, played a crucial role in the production and development of penicillin from this fungus.