The correct option is The origin of the greased cartridge rumour involving a Khalasi and a Brahmin sepoy..
Explanation
The immediate trigger for the Revolt of 1857 was the introduction of the Enfield Rifle and the suspicion among sepoys regarding the grease used in its cartridges. The "Captain Wright" report is the primary historical evidence documenting the origin of this rumour.
Historical Context and Analysis:
- Origin of the Report: In January 1857, Captain Wright was an officer stationed at the Rifle Instruction Depot in Dum Dum, near Calcutta.
- The Incident: Captain Wright reported an incident involving a high-caste Brahmin sepoy and a low-caste Khalasi (laborer) employed at the magazine. The Khalasi asked the sepoy for water from his lota (water pot). The sepoy refused, stating that his caste would be defiled by the touch of a lower caste.
- The Retort: The Khalasi reportedly retorted that the sepoy’s caste pride would soon be irrelevant, as the British government was manufacturing cartridges greased with the fat of cows and pigs, which all sepoys would be required to bite.
- Significance: Captain Wright officially conveyed this conversation to his superior, Major Bontein. This report is historically significant as it marks the first official record of the "greased cartridge" rumour, which subsequently spread to Barrackpore, Meerut, and Delhi, igniting the rebellion.
Key Takeaway: Captain Wright's report (January 1857) detailed the Khalasi-Brahmin altercation at the Dum Dum depot, serving as the first documented source of the rumour that Enfield cartridges were greased with cow and pig fat.