When the Indian National Congress was founded, Lord Dufferin was the Viceroy of India. The Viceroy was the highest-ranking official representing the British government in India.

Option 1, Lord Lytton, was the Viceroy of India from 1876 to 1880, which was before the Indian National Congress was founded in 1885. Therefore, option 1 is incorrect.

Option 2, Lord Ripon, served as the Viceroy of India from 1880 to 1884, which overlaps with the founding of the Indian National Congress. However, he was not the Viceroy at the time of the founding. Hence, option 2 is also incorrect.

Option 3, Lord Dufferin, was the Viceroy of India from 1884 to 1888. He was the Viceroy when the Indian National Congress was founded in 1885. Therefore, option 3 is the correct answer.

Option 4, Lord Curzon, became the Viceroy of India in 1899, which is long after the Indian National Congress was founded. Thus, option 4 is incorrect.

In conclusion, Lord Dufferin was the Viceroy of India when