Explanation
Using materials with a high recycled content is a strategy to reduce construction waste. Recycled content materials are made from pre-consumer or post-consumer waste that has been diverted from landfills or incinerators and reprocessed into new materials. Using recycled content materials reduces the demand for virgin materials, saves energy and resources, and prevents waste generation. The other options are not strategies to reduce construction waste. Performing a waste stream audit is a strategy to measure and analyze the types and quantities of waste generated by a building or project. Developing a construction waste management policy is a strategy to establish goals and procedures for diverting construction waste from landfills or incinerators. Hiring a consultant to sort construction waste off site is a strategy to outsource the responsibility of separating recyclable or reusable materials from construction waste, but it does not necessarily reduce the amount of waste generated. References: LEED Green Associate Candidate Handbook, page 26; USGBC, [Materials and Resources], page 2.

Explanation
Sizing the building appropriately means designing the building to meet the needs and expectations of the occupants, without creating excess space that would require more energy to heat, cool, and light. This strategy reduces the energy demand of the building and also saves on construction costs and materials.
References:
LEED v4 for Building Design and Construction, p. 36
LEED Green Associate Candidate Handbook, p. 11

A high-efficiency HVAC (Heating, Ventilation, and Air Conditioning) system can directly reduce a building's greenhouse gas emissions by using less energy than a standard system. Since most energy production involves the burning of fossil fuels, which releases greenhouse gases, using less energy results in fewer emissions. Reference: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources

To maintain the LEED Green Associate credential, you must earn 30 continuing education hours every two years, with at least six of those hours being LEED specific. This requirement ensures that LEED Green Associates stay up-to-date with the latest developments in green building practices and LEED rating systems. References: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources

Conserve and restore habitat is the correct answer because LEED Sustainable Sites encourages project teams to protect existing natural features and restore disturbed site areas with native or adaptive vegetation. This helps preserve biodiversity, support ecosystem services, protect sensitive ecological areas, and reduce harm from development. Mixed-use development can support smart growth and transportation efficiency, but it does not directly safeguard ecologically important areas. Constructing near prime farmland is not a good LEED strategy because prime farmland is considered sensitive land that should generally be protected from development. Increasing the parking footprint expands hardscape, increases runoff, and can damage habitat. Habitat conservation and restoration support LEED goals related to biodiversity, open space, natural systems, and responsible site development.