In EDGE, certain measures are mandatory to ensure a baseline level of resource efficiency, while others are optional depending on the project’s goals. The EDGE User Guide specifies mandatory measures for certification: "To achieve EDGE certification, projects must meet minimum requirements, including mandatory measures such as insulation of the roof to reduce heat gain or loss, ensuring a basic level of energy efficiency across all building typologies in climates where thermal performance is relevant" (EDGE User Guide, Section 4.1: Insulation Measures). Option B, insulation of roof, is identified as a required measure in EDGE, particularly in climates where heating or cooling loads are significant, which applies to most regions. Option A (green roof) is an optional measure, not mandatory: "Green roofs are an optional measure in EDGE, contributing to energy and water savings but not required for certification" (EDGE User Guide, Section 4.5: Additional Energy Measures). Option C (lighting controls) is also optional, as EDGE allows flexibility in lighting strategies: "Lighting controls, such as occupancy sensors, are optional measures that can enhance energy savings but are not mandatory" (EDGE User Guide, Section 4.4: Lighting Efficiency Measures). Option D (efficient lighting for internal areas) is encouraged but not required: "Efficient lighting for internal areas (EEM22) is an optional measure, requiring at least 90% of lamps to be efficient, but projects can achieve certification without it if other energy measures meet the 20% savings threshold" (EDGE User Guide, Section 4.4: Lighting Efficiency Measures). The EDGE Certification Protocol reinforces this: "Mandatory measures like roof insulation ensure a minimum standard of energy efficiency, while measures like green roofs, lighting controls, and efficient lighting are optional and contribute to overall savings" (EDGE Certification Protocol, Section 2.2: Certification Requirements). Therefore, insulation of the roof (Option B) is the required measure among the options.