Asmall crack occurs at the base of a 15.0-m-high dam. the effective area through which water leaves is 3.90 × 10-3 m2.
(a) ignoring viscous losses, what is the speed of water flowing through the crack?
(b) how many cubic meters per second of water leave the dam?

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