4) A certain curve is banked at an angle of 37º and has a radius of 35 m. A car with a mass 120 is traveling at a speed of 12 m/s when it enters the curve.
Does the car make it around the curve without slipping?

Independent variable is something that is changed in a experiment. 

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