A4000 kg truck is parked on a 15 degree slope. how big is the friction force on the truck? the coefficient of static friction between the tires and the road is 0.90.

The answer is d) by requesting advice on science internet sites

From negative to negative

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