A force of 50 N is applied to a screwdriver to pry the lid off a can of paint. The screwdriver applies 85 N of force to the lid What is the mechanical advantage of the screwdriver?

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

Answerit increases at a steady rate;