The constitutional provision that incorporated Sikkim into the Indian Union is:

The correct answer is: c) Article 371A

Article 371A of the Indian Constitution is a special provision that applies to the state of Sikkim. It was inserted into the Constitution by the 36th Amendment Act, 1975, after Sikkim became an Indian state in 1975.

Article 371A provides for special safeguards for the people of Sikkim in matters of religion, language, culture, and economic development. It also provides for the appointment of a Governor for Sikkim who is to be appointed by the President of India on the advice of the Central Government.

The other options are incorrect because:

• Article 360 is a provision of the Indian Constitution that deals with financial emergency.
• Article 370 is a provision of the Indian Constitution that deals with the special status of Jammu and Kashmir.
• Article 371F is a provision of the Indian Constitution that deals with the special status of Nagaland.