You have an extension lead with three appliances that are permanently plugged in. The appliances need currents, of 2 A, 1 A and 0.5 A. Which would be the best fuse to use in the extension lead?
20 A
5A
ЗА
14 A

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