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: Dental
Which is not a first-generation chemical plaque control agent? 
Select and explain. 
A. Phenol, B. Antibiotics, C. CHX, D. Sanguinarine
C: CHX
Answer: C: CHX 
Explanation: Chemical plaque control agents
First generation:

Eg: Antibiotics, phenol quaternary ammonium compounds and sanguinarine.

Second generation:

Bisbiguanides (Chlorhexidine)

Third generation

Delmopinol