En un recipiente con agua abierto a la atmósfera en su parte superior tiene un pequeño orificio en la parte interior a 6m por debajo de la superficie del liquido A)con que velocidad sale el agua por el orificio? B)si el diametro del orificio es de 1,9cm ¿cual es el el caudal del agua que sale del recipiente ?

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