Un diapason con una frecuencia de 400hz se aleja de un observador y al mismo tiempo se acerca a una pared plana con una rapidez de 2m/seg. Encuentre cual seria la frecuencia o parentesis a.- de las ondas sonoras no reflejados que van directamente al observador

What are you trying to ask?

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

Ibelieve the answer is either b or c, but i'm leaning more towards c.hope my answer has you : )

Ibelieve the answer is d. macula  hope my answer has you : )