Simple machines make work easier. most simple machines reduce the amount of effort force needed to move an object. this cart has a set of wheels. the wheels are actually simple machines: the wheel and axle. how can we change these wheels to decrease the amount of effort force needed to move the wagon?

a) use a larger wheel and axle.
b) make the radius of the axle larger in diameter.
c) make the radius of the wheel larger in diameter.
d) make the radius of the wheel smaller in diameter. ( d is incorrect. )