Some of the prominent Public Sector Undertakings (PSUs) in across various sectors include:

1. Oil and Natural Gas Corporation (ONGC) - Energy
2. Indian Oil Corporation (IOC) - Energy
3. Bharat Heavy Electricals Limited (BHEL) - Engineering . Coal India Limited (CIL) - Mining
4. Steel Authority of India Limited (SAIL) - Steel
5. Oil Limited (OIL) - Energy
6. NTP Limited - Energy
7. Bharat Electronics Limited (BEL) Electronics
8. Hindustan Aeronautics Limited (HAL) - Aerospace
9. Grid Corporation of India - Energy

These are just a few examples, but there are many more PSUs operating in India across various industries.

Some of the key Public Sector Undertakings (PSUs) in the Indian railway sector include:

1. Indian Railways
2. Rail Vikas Nigam Limited (RVNL)
3. Dedicated Freight Corridor Corporation of India (DFCCIL)
4. Ircon International Limited
5. RailTel Corporation of India
6. Konkan Railway Corporation Limited (KRCL)

These PSUs play important roles in the development, maintenance, and modernization of the Indian railway network.

In the road and infrastructure sector in India, some of the significant Public Sector Undertakings (PSUs):

1. National Highways Authority of India (NHAI)
2. National Buildings Construction Corporation (NBCC)
3. Engineers India Limited (EIL)
4. Central Public Works Department (CPWD)
5. Indian Railway Construction Company Limited (IRCON)
6. Power Grid Corporation of India (POWERGRID) - involved in infrastructure projects including power transmission, but also plays a role in supporting infrastructure development.

These PSUs are involved in the construction, maintenance, and development of roads, highways, bridges, and other critical infrastructure projects across the country.

In the metal sector in India, there are several Public Sector Undertakings (PSUs) involved in mining, processing, and marketing of various metals. Some of the notable PSUs in this sector include:

1. National Company Limited (NALCO) - primarily involved in the mining and refining of bauxite and production of alumina and aluminum.
2. Hindustan Copper Limited (HCL) - engaged in the exploration, mining production, and marketing of copper.
3. Steel Authority of India Limited (SAIL) - a producer of steel, operating integrated steel plants across India.
4. National Mineral Development (NMDC) - involved in the exploration of a wide of minerals including iron ore, copper, rock phosphate, lime stone, dolomite, and.

These PSUs play a crucial role in the metal sector, contributing to the development and growth of India's industrial and infrastructural landscape.

In the manufacturing sector, several key Public Sector Undertakings (PSUs) in India are involved in production, processing, and promotion of a wide range of manufactured goods. Some significant PSUs in the manufacturing sector include:

1. Bharat Earth Movers Limited (BEML) - Specializes in manufacturing heavy equipment for mining, construction, rail, defense sectors, and heavy engineering products.
2. Bharat Dynamics Limited (BDL) - Primarily engaged in the manufacturing of guided missiles and allied defense equipment.
3. Mazagon Dock Shipbuilders Limited - A premier shipyard constructing warships and submarines for the Indian Navy and offshore platforms and associated vessels for offshore oil drilling.
4. Garden Reach Shipbuilders & Engineers Ltd (GRSE) - Involved in the construction of warships various vessels for the Indian Navy and Coast Guard.

These PS contribute significantly to the manufacturing sector, playing a crucial role in the development of indigenous capabilities in various strategic and industrial domains.

In the water and waste management sector in India, several Public Sector Undertakings (PSUs) are responsible for water resource management, sanitation, and waste disposal. Some key PSUs in this sector include:

1. National Power Corporation (NTPC) - While primarily an energy company, NTP has initiatives for water and environment management, including waste management and conservation of water resources in and around its plants.
2. National Environmental Engineering Research Institute (NEERI) - Though not a traditional PSU, NEERI is a prominent research institute dedicated to environmental science and engineering, particularly in the areas of wastewater management and environmental sustainability.
3. Central Pollution Control (CPCB) - Responsible for promoting cleanliness of streams and wells, and also for improving the quality of air in the country.

These PSUs, along with other government bodies and organizations, play a vital role in managing and conserving water resources and addressing the challenges associated with waste management in India.

In the mining sector in, several prominent Public Sector Undertakings (PSUs) are involved in the exploration, extraction, and processing of a variety of minerals. Some noteworthy PSUs in the mining sector include:

1. India Limited (CIL) – The largest coal-producing company in the world, responsible for around 83% of India's coal output.
2. National Mineral Development Corporation (NMDC) – Engaged in the exploration of a wide range of minerals, including iron ore, copper, rock phosphate, lime stone, dolomite, and more.
3. MOIL Limited (formerly Manganese Ore India Limited) – A leading producer of manganese ore, involved in mining and processing of manganese ore.
4. Hindustan Copper Limited (HCL) – A mining and metal company, involved in exploration, mining, and production of copper.

These PSUs play a crucial role in fulfilling the country's demand for essential minerals and contribute significantly to the growth and development of the mining sector in India.