Jason took 6 hours to travel 540 km. For the first 140 km, he took 2 hours. What was his average speed for the rest of the journey. I would really like the explanation as well so I understand how you got that answer.

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

Wikis are written or edited by someone

Assuming you're referring to significant figures, none of these answer choices are shown to be zero as significant digits. did you, by chance, forget to add something?