Hail comes straight down at a mass rate of m/δt = 0.050 kg/s and an initial velocity of v0 = -15 m/s and strikes the roof perpendicularly. unlike rain, hail usually does not come to rest after striking a surface. instead, the hailstones bounce off the roof of the car. suppose that the hail bounces off the roof of the car with a velocity of +15 m/s. ignoring the weight of the hailstones, calculate the force exerted by the hail on the roof.

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