My son had this assignment and it is totally confusing to me.

Question

This is the info provided:
4.5-V lightbulb
and 3 batteries that are 1.5 V each

Knowing Ohm's law: voltage (in volts) =current (in amps) x resistance (in ohms) or V=IR. Determine in which circuit the voltage was the largest and explain how you know this?

I am drawing a blank and am assuming that the circuit with all three batteries would provide the most since they have the full power then. I am not sure about this and don't know does this mean he needs to figure out what the V=IR is?