Detection of inducible clindamycin resistance using the D test

Commercially available erythromycin and clindamycin disks are placed in a standardized fashion on an agar plate inoculated with a standardized inoculum of the test organism. The plates are incubated for 16 to 24 hours and then visually inspected.
(A) Flattening of the clindamycin zone of inhibition (D-zone) adjacent to the erythromycin disk, indicating inducible clindamycin resistance.
(B) An isolate that is erythromycin-resistant but clindamycin-susceptible.
(C) An isolate that is susceptible to both clindamycin and erythromycin.
(D) An isolate with constitutive resistance to both clindamycin and erythromycin.