The answer is d. an antibiotic.
Ciprofloxacin is a fluoroquinolone broad-spectrum antibiotic developed in 1987 and used to treat a wide variety of bacterial infections. It is effective against both gram-negative and gram-positive bacteria. It is commonly used to treat respiratory, urinary, gastrointestinal, and abdominal infections. In recent years a lot of bacteria has developed resistance to the drug due to the heavily irresponsible use to treat minor infections.