The correct answer is option 4, National Human Rights Commission. The National Human Rights Commission is not a constitutional body in India. A constitutional body refers to an institution that is mentioned and established in the Constitution of India.

Let`s now examine the other options:

Option 1: Comptroller and Auditor General (CAG) is a constitutional body in India. It is mentioned in Article 148 of the Constitution and is responsible for auditing the accounts of the government and ensuring transparency and accountability.

Option 2: National Commissioner for Linguistic Minorities is also a constitutional body in India. It is mentioned in Article 350B of the Constitution and is responsible for safeguarding the rights of linguistic minorities.

Option 3: National Commission for Scheduled Castes is yet another constitutional body in India. It is mentioned in Article 338 of the Constitution and is responsible for protecting the rights and promoting the welfare of the scheduled castes.

In conclusion, the National Human Rights Commission is not a constitutional body in India. It is important to understand the distinction between constitutional bodies and non-constitutional bodies to have a clear understanding of the institutions mentioned in the Indian Constitution.