The right option is; c. resistant
An antimicrobial disk on a Kirby-Bauer plate that shows no zone of inhibition indicates that the microbe being tested is resistant to the drug.
Kirby-Bauer test is a test that uses antimicrobial disks or wafers to determine whether specific bacteria are susceptible or resistant to specific antibiotics. The zone of inhibition which is an empty area on the Kirby-Bauer plate that surrounds an antibiotic disk shows whether the antibiotic worked against the specific organism. The larger the zone of inhibition, the more effective the antibiotics is but if the plate indicates no zone of inhibition, the tested organism is resistant or is not susceptible to that antibiotic (drug). This means that the organism will not respond to that particular drug regardless of the dosage and the area of the infection.
