A50-g ice cube at 0ºc is submerged into a container of liquid nitrogen. how many kg of nitrogen evaporates if it is at its boiling point of 77k and has a latent heat of vaporization of 200 kj/kg? the specific heat of ice is 2100 j/(kg ºc).

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