Final answer:
C. Class III Class III is the categorized class where combustible fibers are always present, as defined by the National Electric Code.
Step-by-step explanation:
The class of classified location where combustible fibers are always present is Class III. According to the National Electric Code (NEC), hazardous locations where combustible fibers or flyings are manufactured, handled, or used fall under the Class III category. These locations could include textile mills, cotton gins, and flax processing plants. The main concern in Class III locations is to prevent the accumulation of fibers which could ignite and cause a fire hazard. Devices and wiring methods used in these areas are designed to prevent the ignition of the fibers.
C. Class IIIClass III locations are those where easily ignitable fibers or materials producing combustible flyings are handled, manufactured, or used, but which are not likely to be suspended in the air in quantities sufficient to produce explosive or ignitable mixtures. Since combustible fibers are always present in this case, Class III is not the correct class.D. Class IVClass IV locations are those where easily ignitable fibers are stored or handled, but where such fibers are not likely tbe in suspension in the air. Therefore, Class IV is not the correct class for locations where combustible fibers are always present.Based on these explanations, the correct answer is Class II.