Answer:
Circuit A
Explanation:
Let voltage of one battery be V
The circuit at the top has an overall voltage of [tex]V[/tex]
Circuit A is in series which means the overall voltage is [tex]V+V=2V[/tex]
Circuit B is the same as Circuit C where both are parallel to the bulb.
The overall voltage is [tex]\frac{1}{V}+ \frac{1}{V} = \frac{2}{V}[/tex]
Circuit D will not work as the negative terminal of the battery are touching one another thus it impedes the electron flow in the circuit