Assertion (A): The concept of National Integration involves political, economic, social, cultural and psychological dimensions and inter-relation between them. This statement is true. National integration is a multifaceted concept encompassing various aspects of a nation's life and the harmonious coexistence of its people. Reason (R): The National Integration Council was constituted in 1961 on the principle of ‘Unity in Diversity’. This statement is also true. The NIC was indeed established in 1961 to address issues related to national integration, and the guiding principle of 'Unity in Diversity' is central to India's identity. Explanation: The establishment of the National Integration Council in 1961 was a direct response to the need to address the challenges and promote the concept of National Integration, which is based on the principle of 'Unity in Diversity'. Therefore, the Reason correctly explains the Assertion.