A sphere of radius 5.00 cm c m carries charge 3.00 nC n C . Calculate the electric-field magnitude at a distance 4.00 cm c m from the center of the sphere and at a distance 6.00 cm c m from the center of the sphere if the sphere is a solid insulator with the charge spread uniformly throughout its volume.

Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current