The Partition of Bengal made by Lord Curzon in 1905 lasted until

(a) the First World War when Indian troops were needed by the British and the partition was ended
(b) King George V abrogated Curzon's Act at the Royal Durbar in Delhi in 1911 ✓ UPSC's answer
(c) Gandhiji launched his Civil Disobedience Movement
(d) the Partition of India in 1947 when East Bengal became East Pakistan

Why the answer is (b)

• Curzon's partition of Bengal (October 1905) provoked the Swadeshi movement; under its pressure the British annulled the partition, and King George V announced the reunification of Bengal (and the shift of the capital to Delhi) at the Delhi Durbar of December 1911 — option (b).

• Bihar, Orissa and Assam were separated instead; Bengal was again divided only in 1947.

• Hence option (b).

Why the other options are wrong

(a) the First World War when Indian troops were needed by the British and the partition was…: The annulment came in 1911, before the War.
(c) Gandhiji launched his Civil Disobedience Movement: Civil Disobedience (1930) was long after.
(d) the Partition of India in 1947 when East Bengal became East Pakistan: The 1905 partition was undone in 1911, decades before 1947.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2014, held on 24 August 2014. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.