Okay, so if dna is in the chromosome how many chromosomes do we have

OK
We have 46 chromosomes 

H0P3 It H3LPS :)

A human has 2 types of chromosomes x and y

23 x
23 y

In total we have 46

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

Iwould think it would be efficiency.