Ixchelt burns her tongue when she takes a sip of hot coffee from her mug. Which part of this example represents heat?
the thermal energy moving from the coffee to her tongue
the thermal energy moving from her tongue to the coffee
her coffee
her tongue

Efficiency is an act of doing something

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