Final answer:
Salvarsan, a drug used to treat syphilis, was formulated from the red dye prontosil.
Step-by-step explanation:
Salvarsan, a drug used to treat syphilis, was formulated from the red dye prontosil.
Salvarsan was not discovered as a product of Penicillium notatum. Penicillin, the first natural antibiotic, was discovered as a product of Penicillium notatum by Alexander Fleming.
Salvarsan was not first discovered by Robert Koch. It was discovered by Sahachiro Hatta, who was assistant to Paul Ehrlich.
Therefore, the correct answer is A. Salvarsan was formulated from the red dye prontosil.