Which type of hydraulic tool generates extending and retracting forces to move material?

The correct answer is extension rams because they are specifically designed to generate extending and retracting forces that can effectively move material. These tools utilize hydraulic pressure to extend their length for applications such as lifting or pushing objects apart. In rescue operations, for instance, extension rams can create space in collapsed structures, allowing for the rescue of trapped individuals.

While cutter tools are designed to slice through materials, they do not primarily focus on moving objects but rather on cutting through them. Spreader tools also apply force but are mainly used to widen or separate objects rather than extend or retract. Power units serve to supply the hydraulic pressure necessary for various tools but do not have the capability to move materials on their own. Thus, extension rams align perfectly with the function of generating the required forces to move materials.