Two point sources, S1 and S2, oscillating in phase send waves into the air at the same wavelength, 1.98m. Given that there is a nodal point where the two waves overlap, find the smallest corresponding path length difference.

Is this a question of an answer

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