The correct answer is: C. The Congress had observed it as the Independence Day in 1930.
On January 26, 1930, the Indian National Congress adopted the Purna Swaraj resolution, declaring India’s independence from British rule. This day was subsequently observed as Independence Day by the Congress and its supporters. After India gained independence in 1947, January 26 was chosen as the date for the inauguration of the Constitution. This was done in recognition of the significance of the day in the history of the Indian independence movement.
The other options are incorrect. Option A is incorrect because there is no evidence to suggest that January 26 was considered to be an auspicious day. Option B is incorrect because the Quit India Movement was started on August 9, 1942. Option D is incorrect because the Congress did observe January 26 as the Independence Day in 1930.