Question

at which point would the circuit need to be severed to prevent all light bulbs from working?
3
3 and 4
4
1 or 2

Explanation:

The circuit has three bulbs in parallel, connected to the battery via points 1/2 (positive side) and the lower connections (negative side). To stop all bulbs, we must break the shared path that supplies all branches. Points 1 and 2 are part of the main positive supply line common to all parallel branches. Severing either 1 or 2 cuts off power to every bulb's branch. Severing 3 or 4 only stops individual bulbs, not all.

Answer:

1 or 2