The correct answer is (a) Lord Canning.
Lord Canning was the Governor-General of India from 1856 to 1862. He was the first Viceroy of India after the Indian Rebellion of 1857. He made Allahabad the emergency headquarters in 1857 because it was a strategically important location. It was located on the banks of the Ganges River, and it was close to the Mughal capital of Agra. Allahabad was also a major military center, and it had a large population of British troops.
Lord Cornwallis was the Governor-General of India from 1786 to 1793. He was a British general who is best known for his victory over the French at the Battle of Yorktown in 1781. He was not the Governor-General of India in 1857.
Lord Wellesley was the Governor-General of India from 1798 to 1805. He was a British statesman who is best known for his expansion of the British Empire in India. He was not the Governor-General of India in 1857.
Lord William Bentinck was the Governor-General of India from 1828 to 1835. He was a British statesman who is best known for his reforms in India, including the abolition of sati and the introduction of English education. He was not the Governor-General of India in 1857.