C.3 - Mutation of the Quinolone Resistance-Determining Region (QRDR) of the DNA gyrase.
D
D.4 - Drug efflux.
正确答案：
Resistance to fluoroquinolones arises as a result of alterations in the target enzymes (DNA gyrase and topoisomerase IV) and changes in drug entry or efflux. Classical mutations are observed first in the more susceptible target: DNA gyrase.
