Final answer:
RFID chips are used in a variety of tracking applications, including livestock monitoring, marathon runners' timing, and retail inventory management, demonstrating the wide range of tracking capabilities available today.
Step-by-step explanation:
RFID chips are a versatile technology used in various applications for tracking and identification purposes. The question asks in which scenarios RFID chips have been used. The answer is D. All of the options. RFID chips can indeed be used to track livestock, ensuring that farmers can monitor the location and health of their animals. They are also used to track marathon runners' times, providing accurate timings for each runner as they cross checkpoints. Finally, RFID technology is commonly used to track inventory at retailers, which helps in managing stock levels efficiently. This technology showcases how it has become easier to track and monitor both objects and individuals, as also demonstrated by other systems like electronic toll collection and GPS.