Concept: The electric bulb glows when the current makes its filament hot. If the current provided is not sufficient to make it hot, the bulb will not glow. Magnetic effect of current: The current has a magnetic effect and it attracts magnetic materials just as another magnet. LED Bulb: Light Emitting Diodes are devices that can glow even in very small currents. Explanation: The Electric bulb will not glow if sufficient current is not provided. The lemon-water solution is a good conductor of electricity but a lesser good conductor as compared to metals. So, sometimes bulb may not glow. In that case, we can use a magnetic tester. A magnetic needle is brought near the wires. If deflection is observed, we can say that the current is flowing and lemon - water conducts electricity. Another way to check is using a light-emitting diode. The LED bulb requires much less current than an electric bulb to glow. So, if LED is glowing, we can say there is a current. Therefore, Both B and C options can be used. Additional Information LED [ alt="Reported 15-7-2021 nikhil D2" src="//storage.googleapis.com/tb-img/production/21/07/Reported_15-7-2021_nikhil_D2.PNG" style="width: 78px; height: 229px;"> LED has two wires attached to it called leads. The larger lead is connected to the positive terminal of the battery and the smaller one is connected to the negative terminal of the battery.