If a rock is thrown vertically upward from the surface of mars with velocity 15 mys, its height after t seconds is h − 15t 2 1.86t2. (a) what is the velocity of the rock after 2 s? (b) what is the velocity of the rock when its height is 25 m on its way up? on its way down?

Hi, your answer is not correct. this is a cumulative  

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