This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Drug to be avoided in a patient allergic to penicillin is: 
Select and explain. 
A. Sulphonamide, B. Tetracycline, C. Ampicillin, D. Chloramphenicol
C: Ampicillin
Answer: C: Ampicillin 
Explanation: None