Which of the following elements of the preamble assures the dignity of the individual and the unity and integrity of the Nation?

As per Preamble to the Constitution, 1950- WE, THE PEOPLE OF INDIA, having solemnly resolved to constitute India into a 1 [SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC] and to secure to all its citizens: JUSTICE, social, economic and political; LIBERTY of thought, expression, belief, faith and worship; EQUALITY of status and of opportunity; and to promote among them all FRATERNITY assuring the dignity of the individual and the [unity and integrity of the Nation]; IN OUR CONSTITUENT ASSEMBLY this twenty-sixth day of November, 1949, do HEREBY ADOPT, ENACT AND GIVE TO OURSELVES THIS CONSTITUTION.