Which of the following is a mandatory requirement under LEED v4 for BD+C certification?

Fundamental commissioning and verification is indeed a mandatory requirement under LEED v4 for Building Design and Construction (BD+C) certification. This process ensures that building systems are designed, installed, and calibrated to operate as intended. The commissioning process involves verifying and documenting that the building's systems function correctly to achieve the owner's project requirements, which is crucial for optimizing energy performance and providing a high-quality environment for occupants.

In the context of LEED, this requirement serves to enhance the reliability of the building's performance post-construction, ultimately contributing to sustainability goals. It ensures that energy and water efficiency measures are not only designed but also executed properly, fostering a thorough operational understanding of the systems involved.

The other choices, while related to sustainable building practices, do not represent mandatory requirements for LEED v4 certification in the same way. Rainwater management is encouraged but is not mandatory. Similarly, having a Construction Indoor Air Quality (IAQ) management plan is part of best practices but is not a requirement for certification. Lastly, while having a LEED accredited professional can be beneficial and guide the project towards better sustainability practices, it is not a requirement to achieve BD+C certification under LEED v4.