Option 1: Lord Dalhousie was the Governor-general of India before the Revolt of 1857. He is known for introducing various reforms like the Doctrine of Lapse and the construction of railways in India. However, he was not in office during the Revolt of 1857.

Option 2: Lord Canning was the Governor-general of India during the Revolt of 1857. He had taken office in 1856 and his tenure was marked by the outbreak of the rebellion. He faced immense challenges in suppressing the revolt and restoring British control over India.

Option 3: Lord Mayo was the Governor-general of India after the Revolt of 1857, from 1869 to 1872. He undertook several administrative and economic reforms during his time in office.

Option 4: Lord Ripon was the Governor-general of India from 1880 to 1884, decades after the Revolt of 1857. He is known for introducing the Vernacular Press Act and the Local Self-Government Act, among other reforms.

The correct answer is Option 2, Lord Canning, as he was the Governor-general of India during the Revolt of 1857.