Final answer:
The most serious adverse reaction to penicillin is c. Anaphylaxis, which is a potentially life-threatening condition requiring immediate medical attention.
Step-by-step explanation:
The most serious adverse reaction to penicillin is c. Anaphylaxis. Anaphylaxis is a severe, potentially life-threatening allergic reaction that can occur in individuals who are hypersensitive to a substance, such as penicillin. In some cases, anaphylaxis can lead to a coma or even death if not treated promptly with emergency care. Penicillin is an antibiotic that is commonly used to treat bacterial infections, and while it is often well-tolerated, it can cause a range of allergic reactions. Anaphylaxis is the most severe form of allergic reaction and requires immediate medical attention.