Abullet fired straight through a board  0.10  m  thick strikes the board with a speed of  480  m/s  and emerges with a speed of  310  m  .
part a
what is the  x  component of the average acceleration of the bullet while in the board? the positive  x  direction is the initial direction of motion of the bullet.
express your answer with the appropriate units.

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