The correct answer is B) functions like a switching device and controls relatively high load current. A silicon controlled rectifier (SCR) is a solid-state device that functions primarily as a switching device. SCRs are capable of controlling and switching relatively high load currents, making them suitable for applications such as power control, motor control, and other industrial applications. They can be used to turn on and off high-power circuits, making them an effective switching device. The other options are incorrect because SCRs are not typically used as amplifiers (options A and C), and they are not designed to control low load currents (options C and D). The key function of an SCR is to act as a switching device for high-power applications.