Question

which switch has been turned on (closed) for the circuit to work?abcwhich switch has been turned on (closed) for lightbulb 1 to work?

Explanation:

Step1: Analyze first circuit question

For the entire circuit to work, the main path from the battery must be closed. Switch A is in the main circuit that connects the battery to the rest of the components. If A is open, no current flows at all, regardless of B and C.

Step2: Analyze second circuit question

For lightbulb 1 to work, current needs to flow through it. The path for bulb 1 goes through the main switch A and switch B (which directly connects to bulb 1). Closing A allows current into the circuit, and closing B completes the loop for bulb 1.

Answer:

1. For "Which switch has been turned on (closed) for the circuit to work?":

A. A

1. For "Which switch has been turned on (closed) for lightbulb 1 to work?":

A. A, B. B