Water closets, also known as toilets, are fixtures that use water to flush human waste into a sewer or septic system. The unit of measure for water closets is gallons (liters) per flush, which indicates the amount of water used for each flushing cycle. The water efficiency of water closets can vary depending on the design, technology, and regulation of the fixture. The LEED rating system encourages the use of water-efficient fixtures that reduce water consumption and wastewater generation12. Reference: LEED v4 Green Associate Candidate Handbook1, EPA's WaterSense Toilets2

According to a study completed by the Heschong Mahone Group, providing increased daylighting in schools can improve student test scores by 7%-18%. Daylighting is the practice of placing windows, skylights, other openings, and reflective surfaces so that sunlight (direct or indirect) can provide effective internal lighting. Particular attention is given to daylighting while designing a building when the aim is to maximize visual comfort or to reduce energy use. Reference: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources

A 100% vegetated roof coverage best addresses both heat island effect and rainwater runoff from the roof only. A vegetated roof, also known as a green roof, is a layer of living plants that covers the roof surface. A vegetated roof reduces the heat island effect by providing shade, evapotranspiration, and insulation, lowering the roof temperature and the surrounding air temperature. A vegetated roof also reduces rainwater runoff by retaining and absorbing precipitation, decreasing the volume and peak flow of stormwater leaving the roof. The other options are not as effective as a 100% vegetated roof coverage in addressing both heat island effect and rainwater runoff from the roof only. A 100% high-albedo roof reflects more solar radiation than a conventional roof, reducing the heat island effect, but it does not reduce rainwater runoff. A 20% high-albedo and 80% conventional roof has a lower reflectance than a 100% high-albedo roof, resulting in a higher heat island effect, and it does not reduce rainwater runoff either. A 50% standing seam copper and 50% vegetated roof has a lower vegetated area than a 100% vegetated roof, resulting in less shade, evapotranspiration, insulation, retention, and absorption, leading to a higher heat island effect and more rainwater runoff. Reference: LEED Green Associate Candidate Handbook, page 27; USGBC, [Sustainable Sites], page 3.

One of the requirements for the Sustainable Sites Credit: Rainwater Management is that projects must use Green Infrastructure (GI) and Low Impact Development (LID) techniques within the LEED project boundary. GI and LID are design approaches that mimic natural hydrologic processes to manage stormwater runoff at its source. GI and LID techniques include strategies such as rain gardens, bioswales, permeable pavements, green roofs, rain barrels, cisterns, and vegetated buffers. The other options are not requirements for the Sustainable Sites Credit: Rainwater Management. Maximizing open space within the LEED project boundary is a requirement for the Sustainable Sites Credit: Open Space. Calculating the total rainwater runoff for 75th percentile rainfall events is a requirement for the Sustainable Sites Credit: Site Assessment. Using a combination of both structural and non-structural measures to manage a 90th percentile rainfall event is an option for meeting Option 1 of the Sustainable Sites Credit: Rainwater Management. Reference: LEED Green Associate Candidate Handbook, page 27; USGBC, [Sustainable Sites], page 4-5.

Explanation
The term "LEED certified building" is the correct usage according to the U.S. Green Building Council (USGBC). This term indicates that a building has met the standards set by the LEED rating system and has been officially certified by the USGBC. References: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources