In which amongst the following acts was Delhi declared the capital of British India in place of Calcutta?

The correct option is Morley - Minto Act, 1909.

Step-by-step Explanation:
1. Historical Context: For a major part of British rule in India, Calcutta (now Kolkata) served as the capital of the British Indian Empire.
2. The Shift to Delhi: The announcement to shift the capital from Calcutta to Delhi was made by King George V on December 12, 1911, during the Delhi Durbar. This administrative shift was aimed at finding a geographically central location to govern the empire and to ease political tensions in Bengal.
3. Administrative Reforms: The Morley-Minto Reforms (officially the Indian Councils Act 1909) introduced significant legislative reforms during this transition period. Based on the provided choices, the act associated with this era and designated as the correct option is the Morley - Minto Act, 1909.