The British Governor General and Viceroy who served for the longest period in India was

Answer: Option B

The British Governor General and Viceroy who served for the longest period in India was Lord Dalhousie. He held the position from 1848 to 1856, which amounts to a total of 8 years. During his tenure, Lord Dalhousie implemented various significant policies and reforms, including the Doctrine of Lapse and the construction of railways.

Option A: Lord Irwin served as Viceroy from 1926 to 1931.
Option C: Lord Curzon served as Viceroy from 1899 to 1905.
Option D: Lord Linlithgow served as Viceroy from 1936 to 1943, which is a period of 7 years.

Therefore, the correct option is Option B: Lord Dalhousie, who served for the longest period of 8 years as Governor-General of India.