Compare the momentum of a 6,300-kg elephant walking 0.11m/s and a 50 kg dolphine swimming 10.4m/s

Momentum of elephant = 6300 * 0.11 = 693 kg-m/s

Momentum for  the dolphin = 50 * 10.4 =  520 kg-m/s

Difference in momentum = 693 - 520 = 173 kg-m/s

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