Explanation:

- The Treaty of Allahabad was signed in 1765.

- Option 3: 1765 is the correct answer. The treaty marked the transfer of the Diwani rights (revenues and civil administration) of Bengal, Bihar, and Orissa to the British East India Company after the Battle of Buxar.

- Option 1: 1756 is incorrect. In 1756, significant events like the start of the Seven Years’ War and the capture of Calcutta took place.

- Option 2: 1766 is incorrect. It is not associated with the Treaty of Allahabad.

- Option 4: 1770 is incorrect. The Great Bengal Famine occurred in 1770, but it was not the year of the treaty.