Technician exam question T6D10

WhyComponent 2 in figure T-1 controls the flow of current. Component 2 in figure T-1 is the transistor, whose job in this circuit is to control the flow of current from the battery through the lamp based on the small signal applied to its base through the resistor, answer C. It's the lamp, component 3, not the transistor, that gives off light (A), the battery, component 4, that supplies electrical energy (B), and neither this transistor nor any part of this simple lamp-driver circuit converts electrical energy into radio waves (D).