Explanation
Graywater refers to relatively clean wastewater from domestic activities such as washing dishes, laundry, and bathing. Water from lavatory faucets falls into this category. Graywater can be treated and reused for non-potable purposes such as toilet flushing or irrigation, which can help conserve water. References: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources

Explanation
One of the goals of the LEED rating system is to reduce greenhouse gas emissions from transportation by encouraging alternative modes of transportation that are less dependent on fossil fuels. Providing bicycle storage and shower facilities is a strategy that encourages a building's users to use bicycles as a means of transportation, which can reduce vehicle miles traveled, fuel consumption, air pollution, traffic congestion, and parking demand. This strategy can also promote physical activity and health benefits for the users
. References: LEED v4 Green Associate Candidate Handbook, LEED v4 BD+C Reference Guide

Explanation
LEED for Neighborhood Development (LEED ND) is a rating system that aims to inspire and help create better, more sustainable, well-connected neighborhoods1. It looks beyond the scale of buildings to consider entire communities1. One of the main goals of LEED ND is to reduce vehicle miles traveled (VMT) and greenhouse gas emissions by promoting the location and design of neighborhoods that are accessible by foot or public transportation234. Therefore, LEED ND encourages development within and near existing communities or public transportation infrastructure, which is option C.
References: =
LEED certification for neighborhood development
LEED for Neighborhood Development - Wikipedia
LEED for Neighborhood Development - Grow Smart RI
LEED for Neighborhood Development - s3.amazonaws.com

Explanation
Green Seal is a non-profit organization that develops standards and certifies products and services that are environmentally preferable and meet rigorous performance criteria1. Green Seal has standards for various categories of products and services, including custodial products and materials, such as cleaners, degreasers, floor care products, paper products, and hand soaps2. Green Seal-certified custodial products and materials can help achieve credits in the LEED v4 Materials and Resources category, such as Purchasing - Ongoing Consumables34.
References:
About Us | Green Seal1
Standards | Green Seal2
LEED v4: Building Design + Construction Guide - U.S. Green Building Council3 Credit's Supporting LEED's Materials and Resources Category | Legrand4

Explanation
Rainwater is the type of water that would be most useful for landscape irrigation when considering water conservation and water efficient landscaping. Rainwater is water that falls from the sky as precipitation, and it can be collected and stored in tanks, barrels, cisterns, or ponds for later use1. Rainwater is a renewable and free source of water that does not require any treatment or pumping, unlike potable water, which is water that is safe for human consumption and often comes from municipal sources2. Potable water is a scarce and valuable resource that should be conserved for drinking, cooking, and hygiene purposes, rather than for irrigation2. Clean water is a vague term that can refer to any water that is free of contaminants, but it does not necessarily mean that it is potable or suitable for irrigation3. Blackwater is water that contains human or animal waste, such as sewage or toilet water, and it poses a health and environmental risk if used for irrigation without proper treatment4. Therefore, rainwater is the best option for landscape irrigation, as it reduces the demand for potable water, lowers the utility bills, and benefits the plants and soil1.
References:
Rainwater Harvesting for Landscape Irrigation
Potable Water
Clean Water
Blackwater