LEED impact categories are the environmental, social, and economic issues that LEED projects aim to address1. They provide an overview of the market transformation that technical requirements work to achieve, as well as a guide to where points should be assigned2. The categories focus on LEED's social, environmental, and economic goals, and they assess each strategy based on its ability to achieve those goals3.

Explanation
A salvaged wood door from another site qualifies under the Materials and Resources sustainable criteria of materials reuse. Materials reuse is the practice of using existing materials or products for new purposes without altering their form or composition. Materials reuse reduces the demand for virgin materials, saves energy and resources, and prevents waste generation. The other options are not applicable to a salvaged wood door from another site. Certified wood is wood that has been harvested from forests that are managed in an environmentally responsible, socially beneficial, and economically viable manner according to the standards of an accredited certification system such as the Forest Stewardship Council (FSC). Bio-based materials are materials that are derived from plants or animals, such as bamboo, cork, wool, or cotton. Waste diversion is the practice of diverting waste from landfills or incinerators by recycling, reusing, salvaging, or donating materials. References: LEED Green Associate Candidate Handbook, page 28; USGBC, [Materials and Resources], page 4.

Renovating an existing building using recycled and salvaged building materials is an example of a life-cycle approach to development or design. A life-cycle approach is an approach that considers the environmental impacts of a product or a project from cradle to grave, or from extraction of raw materials to disposal or reuse. Renovating an existing building using recycled and salvaged building materials reduces the environmental impacts associated with new construction, such as land use change, resource depletion, energy consumption, waste generation, and greenhouse gas emissions. The LEED Green Associate Candidate Handbook states that one of the intents of the Materials and Resources category is to "promote life-cycle assessment as a means of evaluating environmental impacts" [1, p. 15]. Reference: LEED Green Associate Candidate Handbook, [Life Cycle Assessment | U.S. Department of Energy]