The correct answer is option 3: Lord Canning. During the time of the Revolt of 1857, Lord Canning served as the Governor General of India. It is important to note that the Revolt of 1857, also known as the Indian Rebellion of 1857 or the First War of Independence, was a significant uprising against British colonial rule in India.
Option 1: Lord Hardinge. While Lord Hardinge was a Governor General of India, he served from 1844 to 1848, which was before the Revolt of 1857.
Option 2: Lord Dalhousie. Lord Dalhousie was the Governor General of India from 1848 to 1856, also before the Revolt of 1857.
Option 4: Lord Elgin. Lord Elgin served as the Governor General of India from 1862 to 1863, which was after the Revolt of 1857.
Therefore, the correct answer is option 3: Lord Canning, who was the Governor General when the Revolt of 1857 took place.