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 thatcovers 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. References: LEED Green Associate Candidate Handbook, page 27; USGBC, [Sustainable Sites], page
3.

Paved surfaces absorb and retain heat, increasing local temperatures and contributing to the heat island effect.
LEED encourages mitigating this effect by using materials with high Solar Reflectance Index (SRI) or implementing strategies like green roofs and shaded areas.

The cradle-to-cradle approach to sustainable materials evaluates building materials from extraction to reuse, which means that the materials are considered as part of a continuous cycle of use and regeneration, rather than a linear process of consumption and disposal. The cradle-to-cradle approach aims to eliminate waste and pollution, conserve resources and energy, and create positive impacts for the environment and human health. The cradle-to-cradle approach is based on the principles of eco-effectiveness, which include designing products and systems that are safe and healthy for humans and nature, using renewable energy and clean water, celebrating diversity and creativity, and respecting social and environmental justice12. The cradle-to- cradle approach is also recognized and encouraged by LEED v4, which includes a credit for using products that have achieved Cradle to Cradle certification34.

Drip irrigation is a method of watering plants that delivers water directly to the roots through a network of pipes, tubes, valves, and emitters. Drip irrigation is not a plumbing fixture, but a landscaping technique that can reduce outdoor water use by minimizing evaporation, runoff, and overspray12.
Plumbing fixtures are devices that provide water for various purposes, such as washing, bathing, cooking, or flushing. Plumbing fixtures include urinals, showerheads, kitchen faucets, and other types of faucets, toilets, bidets, and sinks. Plumbing fixtures are subject to indoor water use reduction strategies in LEED certification, such as installing low-flow or high-efficiency models, using automatic sensors or timers, or implementing water reuse systems34.

Regional Priority credits are awarded to encourage projects to address local environmental issues that are of particular importance or concern for the region where the project is located. These issues may include water scarcity, air quality, habitat protection, or human health. Regional Priority credits are not new LEED credits, but rather existing credits that have been identified by regional councils or chapters of USGBC as having higher priority or relevance for their areas. Projects can earn up to four bonus points by achieving Regional Priority credits. References: LEED v4 BD+C Reference Guide, Introduction, page 13; LEED v4 Impact Category and Point Allocation Process Overview1