Parallel circuit allows both lamps to light

Steps:

• Identify the circuit type: lamps connected in parallel to the power source.
• Check connections: both lamps share the same voltage from the battery.
• Verify switch state: closed switch completes the circuit for both branches.
• Apply Ohm's law: current flows through each lamp independently, lighting both.

Why D is correct:

• In a parallel circuit, each lamp has its own path, so both receive voltage and turn on per Kirchhoff's voltage law.

Why the others are wrong:

• A: Both off only if the switch is open or no power source.
• B: Lamp 1 on and 2 off occurs in series with a break in lamp 2's path.
• C: Lamp 1 off and 2 on requires lamp 1 disconnected or faulty.

Final answer: D