Step 1: Understand narrow spectrum antibiotics.
Narrow spectrum antibiotics are effective against a limited range of bacteria, usually either Gram-positive or Gram-negative bacteria only. Step 2: Analyze the given options. (A) Amoxicillin: It is a broad spectrum antibiotic effective against both Gram-positive and Gram-negative bacteria. (B) Ampicillin: It is also a broad spectrum antibiotic. (C) Chloramphenicol: It is a broad spectrum antibiotic with wide antibacterial activity. (D) Penicillin: It is a narrow spectrum antibiotic mainly effective against Gram-positive bacteria. Step 3: Conclusion.
Penicillin is an example of a narrow spectrum antibiotic.