Explanation:

**Aurobindo Ghosh** (later Sri Aurobindo) emerged as a prominent nationalist leader, particularly associated with the extremist faction of the Indian National Congress, largely due to his strong opposition to **the Partition of Bengal** in 1905. This controversial act by Lord Curzon, dividing Bengal for administrative reasons but widely seen as an attempt to weaken Bengali nationalism, sparked widespread protests and the Swadeshi and Boycott movements. Aurobindo became a leading voice advocating for radical nationalism, complete independence (Purna Swaraj), and passive resistance, which brought him into the forefront of the Indian National Movement. Option B is correct. The Surat Split (Option A) in 1907 was a consequence of the ideological differences between the Moderates and Extremists within the Congress, by which time Aurobindo was already a key figure. The Jallianwala Bagh Massacre (Option C) occurred in 1919, much later, by which time Aurobindo had largely retired from active politics and moved to Pondicherry for spiritual pursuits. The famines of 1899-1900 (Option D) caused widespread distress but were not the specific event that propelled Aurobindo into the national movement in the same direct and impactful way as the Partition of Bengal.