Neptune has a mass of 1.0×1026kg1.0×1026kg and is 4.5×109km4.5×109km from the sun with an orbital period of 165 years. planetesimals in the outer primordial solar system 4.5 billion years ago coalesced into neptune over hundreds of millions of years. if the primordial disk that evolved into our present day solar system had a radius of 10111011 km and if the matter that made up these planetesimals that later became neptune was spread out evenly on the edges of it, what was the orbital period of the outer edges of the primordial disk?

The magnets are probably damaged or there not strong enough to attached to the refrigerator

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