The correct answer is Nagpur.
NEERI, the National Environmental Engineering Research Institute, is headquartered in Nagpur, Maharashtra. It works under the Council of Scientific and Industrial Research (CSIR) and focuses on research related to pollution control, waste management, and environmental protection.
NEERI plays an important role in giving scientific advice to the government on issues like air quality, water treatment, and industrial pollution, and it also runs several regional laboratories across India.