Final answer:
Transistor casings are commonly marked with information indicating the manufacturer. These markings refer to datasheets for specifications, ensuring components are used within their safe operating parameters.
Step-by-step explanation:
When transistor casings are marked, one of the important pieces of information indicated is often the manufacturer. The question is asking, among various options, which feature is typically indicated by the markings on a transistor casing. While voltage rating, resistance, and temperature are important characteristics of a transistor's performance, these are not typically listed directly on the device itself. Instead, manufacturers use part numbers or other coding systems that reference a datasheet where detailed specifications can be found, including voltage rating, temperature limits, and other electrical properties. These specifications are critical to ensure that the component is used within its intended operating parameters, to prevent damage or failure. Therefore, the answer to the student's question is c. Manufacturer.
Additional information on electronic components also touches upon concepts such as resistance and how it varies with temperature. For instance, carbon resistors, a semiconductor material known for its negative temperature coefficient, will have a decrease in resistivity, and hence resistance, as temperature increases, which is significant in designing circuits that operate over a range of temperatures.