A circuit contains at minimum

• A. Voltage source, load, and conductors
• B. Voltage source and switch only
• C. Two loads in parallel
• D. Induction coil and capacitor

Answer: (A)

The main idea is what components are needed to form a complete circuit. A circuit requires a source of electrical energy to push current, a path of conductors to carry that current, and a load that uses the energy. If you omit the load, energy has nowhere to go and you don’t have a usable circuit; if you omit the conductors, the energy can’t flow; if you omit the source, there’s no drive to produce current. Therefore, the minimum set is a voltage source, conductors, and a load. The other options add elements that aren’t necessary for the simplest circuit: a switch is a control device, not required to define a circuit; two loads exceed the minimum; and a coil and capacitor describe a specific type of circuit rather than the essential parts needed to complete one.