Among the following, the narrow spectrum antibiotic is: Penicillin G, Ampicillin, Amoxycillin, Chloramphenicol?

Correct option is A. Penicillin G
Benzylpenicillin (Penicillin G) is a narrow-spectrum antibiotic used to treat infections caused by susceptible bacteria. It is a natural penicillin antibiotic that is administered intravenously or intramuscularly due to poor oral absorption. Hence, option A is correct.