What made the 1901 Census particularly significant?

The correct answer is Option 1: It attempted to determine the social hierarchy of castes in particular  regions under the direction of Herbert Risley.

The 1901 Census was particularly important because it attempted not merely to count castes but also to determine their social hierarchy or order of precedence in particular regions of India. This exercise, conducted under Herbert Risley, significantly influenced social perceptions of caste and encouraged many caste groups to claim higher social status.