You are reviewing the following results of a disk- diffusion…

You are reviewing the following results of a disk- diffusion antibiotic susceptibility test on isolated colonies of Streptococcus pneumoniae:                  Antibiotic A: ZI (zone of inhibition) = 0 millimeters Antibiotic B: ZI (zone of inhibition) = 27 millimeters  Antibiotic C: ZI (zone of inhibition) = 9 millimeters Antibiotic D: ZI (zone of inhibition) = 16 millimeters       Which antibiotic is bactericidal?