In the S R Bommai v. Union of India case, the Supreme Court upheld the feature of Secularism as a basic structure of the Constitution of India. Secularism refers to the principle of separation of religion and state. It ensures that the government does not favor any particular religion and treats all religions equally.

Option 1: Liberalism - Though liberalism is an important aspect of the Indian Constitution, it was not specifically identified as a basic structure in the S R Bommai case.

Option 3: Dignity of the human person - Dignity of the human person is a fundamental principle enshrined in the Indian Constitution, but it was not the specific feature upheld in the S R Bommai case.

Option 4: Freedom of religion - While freedom of religion is a key principle, it was not explicitly mentioned as a basic structure in the S R Bommai case.

In summary, the correct answer is option 2, Secularism, as the Supreme Court upheld it as a basic structure of the Constitution of India in the S R Bommai v. Union of India case.