The correct answer is C) 2.0. The mechanical advantage of a tackle system is determined by the number of rope parts supporting the load. In the illustration D029DG, tackle number 2 has two rope parts supporting the load, which results in a mechanical advantage of 2.0. The other answer choices are incorrect because: A) 0.5 is the mechanical advantage of a single sheave block, not a two-part tackle; B) 1.0 would be the mechanical advantage of a single rope supporting the load; and D) 3.0 would be the mechanical advantage of a three-part tackle.