The correct answer is A) Luff tackle. The luff tackle, also known as a luff purchase, is a type of tackle system commonly used on ships and boats. It consists of a single fixed block and a single movable block, with a line or rope threaded between them. This configuration provides a mechanical advantage, allowing the user to apply a greater force with less effort. The other answer choices are incorrect because they do not accurately describe the tackle system depicted in illustration D029DG. A double whip is a different type of tackle system, a one-two tackle refers to a specific configuration with two fixed blocks and one movable block, and a single purchase is a simpler tackle system with only one fixed and one movable block.