Explanation:

All Five activities mentioned above are correct.

• There are 440 districts in India with excessive nitrates in their groundwater as of 2023, an increase from 359 such districts in 2017, according to a report by the Central Groundwater Board (CGWB).

About Central Groundwater Board (CGWB)

• CGWB is a multi-disciplinary scientific organization of the Department of Water Resources, River Development and Ganga Rejuvenation, Ministry of Jal Shakti, Government of India.

• It is the National Apex Agency entrusted with the responsibilities of providing scientific inputs for management, exploration, monitoring, assessment, augmentation, and regulation of groundwater resources of the country.

• Headquarters: Bhujal Bhawan, Faridabad, Haryana. 

The major activities of the CGWB are: 

• National Aquifer mapping and Management (NAQUIM) involving Preparation of Aquifer Maps and Management Plans.

• Groundwater explorations to delineate groundwater worthy areas and potential aquifers.

• Geophysical surveys to delineate groundwater bearing zones, etc.

• Periodic assessment of the country’s groundwater resources.

• Monitoring of groundwater levels and quality through groundwater observation wells.

• Dissemination of Ground Water Data and knowledge.

• Regulation and control of groundwater development and management by CGWA in coordination with State Government Organizations.

• Coordination with State Government with a view to establish benchmark methodologies for groundwater studies.

• R&D studies in ground water sector and application and operationalization of new technologies/techniques for groundwater investigation, development, and management.

• Water conservation and artificial recharge to groundwater.

Hence option 4th is correct.