The correct answer is D. All of the above.
Public sector undertakings (PSUs) are enterprises that are owned and operated by the government. They are established with the objective of promoting social welfare, national interest, and labour welfare.
Social welfare refers to the well-being of the society as a whole. PSUs can promote social welfare by providing essential goods and services at affordable prices, creating employment opportunities, and investing in social infrastructure.
National interest refers to the interests of the nation as a whole. PSUs can promote national interest by ensuring the security of the nation, developing strategic industries, and promoting economic growth.
Labour welfare refers to the well-being of the workers. PSUs can promote labour welfare by providing safe and healthy working conditions, offering fair wages and benefits, and promoting social security.
Some examples of PSUs in India are the Indian Oil Corporation, the Steel Authority of India Limited, and the Bharat Heavy Electricals Limited.