On what basis were people labelled undesirable identified in Nazi thought?

On the basis of Nazi racial and biological prejudices

The governing concept is the Nazi construction of an alleged racial and biological hierarchy. People were labelled undesirable not because of a fair legal process or an objective scientific test, but because Nazi authorities assigned them to groups that the regime considered racially inferior, genetically defective, socially deviant, or politically dangerous. These categories included Jews, Roma and Sinti, people with disabilities, and several other persecuted groups. Option A is correct because it identifies the prejudiced racial and biological assumptions behind the classification. Options B, C, and D imply democratic, rights-based, or lawful standards, whereas Nazi policy deliberately rejected equality and universal human rights.

This is a Class 9 History question. Chapter: Nazism and the Rise of Hitler. Topic: The Nazi Worldview.