Final answer:
Reflective trims may begin to discolor when exposed to temperatures above their thermal stability, generally around 150°C for most reflective materials used in safety applications.
Step-by-step explanation:
The discoloration temperature of reflective trim can depend on the materials used in its construction, but without specific details about the composition of the trim it's difficult to provide a precise temperature at which discoloration occurs. In general, many reflective materials are designed to withstand high temperatures without losing their reflective properties or changing color, but they can start to discolor at very high temperatures.
Reflective trims typically consist of microprismatic elements and a polymer matrix. These materials can begin to degrade and change color when exposed to temperatures above their thermal stability. While it is not possible to answer with certainty without the specific material information, reflective trims used for safety and high-temperature applications are usually designed to withstand temperatures up to around 150°C before they may begin to discolor. Therefore, the likeliest answer, in this case, would be B. 150°C.