Which change will correct the error in the diagram?
changing the N to S
reversing the arrows on the left to point toward the N
changing the Sto N
reversing the arrows on the right to point toward the S

A. to determine if humans can explore mars safely

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