A certain radioisotope has a half-life of approximately 500 years. How long does it take for 4 half-lives to pass?

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

Caused conformity rates to go down. apex ; )

B? i think so but hope that's right and answers your question

Because its not moving at that time hope u understand