THERMAL ENERGY IS SUPPLIED TO A MELTING SOLID AT A CONSTANT RATE OF 2000W. Calculate the mass of the solid changes to liquid to 2.0 minutes. Assume that the specific latent heat of fusion of the solid is 95000 J Kg-1 and the heat exchange with the surroundings may be neglected.

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