Heat naturally flows from an object that has a temperature to an object that has a temperature. Heat can be made to flow in the reverse direction if is done. A machine can never have an efficiency of . This means that heat energy can never be fully converted into energy.

No because a circle or pie graph usually shows percentages you'd need a line graph

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