At a site where the earth's magnetic field has a magnitude of 0.55 gauss (where 1 gauss = 1.00 10-4 t) and points to the north, 68° below the horizontal, a high-voltage power line 152 m in length carries a current of 120 a. determine the magnitude and direction of the magnetic force exerted on this wire, if the orientation of the wire and hence the current is as follows.

Ithink the answer would be 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