Explanation:

The concept of the "Basic Structure" of the Constitution was laid out by the Supreme Court of India in the landmark case of Kesavananda Bharati vs. State of Kerala (1973). The Court held that the basic structure of the Constitution cannot be altered by amendments under Article 368. Over the years, various features have been identified as part of this basic structure:

1. Principles of Natural Justice:  they are not usually listed as part of the basic structure.
2. Limitations upon the amending power conferred by Article 368: This is explicitly part of the basic structure, as per the Kesavananda Bharati case.
3. Secularism: This is also considered part of the basic structure of the Constitution.

So, two out of the three listed items  are generally recognized as part of the basic structure of the Constitution.