Step 1: Background.
In recognition of his work in South Africa, Gandhiji was awarded the title of "Kaiser-e-Hind" by the British government in 1915. However, he later returned the award in protest against British policies.
Step 2: Analyzing the options.
(A) Knight: Incorrect — Gandhiji was never knighted.
(B) Kaiser-e-Hind: Correct — he received this medal in 1915.
(C) Mahatma: This was a title given by the people, not the British government.
(D) All of these: Incorrect, only (B) was officially given by the British.
Step 3: Conclusion.
Thus, the British government gave Gandhiji the title Kaiser-e-Hind.