Answer:
2)
Series circuits = D & E
parallel circuits = C & F
3)
Circuit C is connected in parallel and circuit D is connected in series.
Circuit D and E are the same, despite the switch is located in a different position, they are working in series.
Circuits C and F are the same, they are connected in parallel.
There will be only one bulb in on mode and it is in the circuit F.
Explanation:
In the attached image, we can see a serial circuit and a parallel circuit. Serial circuits are characterized by sharing the same current, if the current step is interrupted (opening the switch), the current will not flow and no element (light bulbs off) will work. When a circuit is connected in parallel, they share the same voltage within the circuit. All resistive elements or bulbs are located between nodes 1 and 2, so they share the same voltage.
The special case are the circuits C and F, both are connected in parallel. But in circuit C the switch is near to the voltage source, therefore when the switch is unplugged there won't be the main current and the bulbs will be off.
In-circuit F, when the switch is off only the bulb near to the switch won't work the other bulb will be working because the main current is passing through it.
