Final answer:
C fibers have poor localization because they are unmyelinated and thin, resulting in slower transmission and less precise localization of sensory information.
Step-by-step explanation:
When discussing the poor localization of sensory information, we refer to how well the location of a stimulus can be determined. Among the two types of nerve fibers you mentioned, C fibers have poor localization. This is because C fibers are unmyelinated and have a thin diameter, leading to a slower transmission of sensory signals, which results in less precise localization of sensations such as pain or temperature. In contrast, A delta fibers are myelinated and transmit signals more rapidly, thus being associated with better localization of stimuli.
Regarding the additional information you provided, a thick myelinated axon (option d) usually corresponds to a faster conduction speed and better localization compared to a thin unmyelinated axon. A bundle of axons in the peripheral nervous system is correctly termed a nerve (option d).