75kg roller skater traveling 15 m/s skids to a stop. if all of the energy is absorbed by his .5 kg aluminum skates, what is the change in temperature?

All i know is that it is higher, maybe try looking up the formula?

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