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
Which of the following is not a broad spectrum antibiotic 
Select and explain. 
A. Tetracycline, B. Chloramphenicol, C. Doxycycline, D. Penicillin G
D: Penicillin G
Answer: D: Penicillin G 
Explanation: None