The correct answer is C) the hauling part leads through the movable block. When a block and tackle is "rove to advantage", it means the hauling part of the rope is passed through the movable block, rather than the standing block. This mechanical advantage allows the user to exert less force to lift or move a heavy load, as the movable block multiplies the pulling force. The other options are incorrect because A) overhauling the blocks does not affect the mechanical advantage, B) the hauling part leading through the standing block would not provide an advantage, and D) having two separate tackle systems attached is a different configuration.