(A) Correct: The 1901 Census of India, led by Herbert Risley, significantly impacted the colonial categorization of caste. Risley's attempt to scientifically classify and rank castes through anthropometric measurements reinforced caste hierarchies and served colonial administrative objectives. Although the question incorrectly references a 1903 census, the focus is on Risley's pivotal role in the 1901 census. He also oversaw the 1911 census.
(B) Incorrect: Colonial censuses gathered substantial data on caste, including social hierarchies, to stratify and manage populations, distribute resources, and solidify existing power structures.
(C) Incorrect: Colonial policies that appeared to benefit lower castes were typically motivated by political strategies like "divide and rule," rather than a genuine commitment to their upliftment.
(D) Incorrect: The Government of India Act of 1935, not 1950, established separate electorates and reservations for specific castes and tribes. The Constitution of India, adopted in 1950, subsequently modified and continued these provisions, officially recognizing Scheduled Castes and Scheduled Tribes and implementing affirmative action measures.