An astronaut travels to a distant star with a speed of 0.56 c relative to Earth. From the astronaut's point of view, the star is 7.6 ly from Earth. On the return trip, the astronaut travels with a speed of 0.88 c relative to Earth. What is the distance covered on the return trip, as measured by the astronaut? Give your answer in light-years.

The answer is b.the gaseous state is electrically positive, while the plasma state is electrically negative. 

What does the start look like

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