Why is it an advantage to the beef producer that beef cattle are foragers?
A. The cattle can graze for grain to eat.
B. It reduces labor as long as there is a good supply of
grasses.
C. The beef will grow much faster with an abundance of
food.
D. It helps to make the herd more fertile.

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

Since the pully is a simple machine so the mechanical advantage is a 1