When two gears mesh, one is called the driver gear because it a) is the follower gear
b) is the smaller gear
c) moves in anticlockwise direction
d) moves in a clockwise direction
e) transmits the power to the driven gear

Because the sun is the biggest and if the sun orbits the earth we will be dead probably

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