The correct answer is B. 1905.
The first successful sugarmill was set-up in Bihar in the year 1905 by the Maharaja of Darbhanga, Sir Kameshwar Singh. The sugarmill was named the Darbhanga Raj Sugar Mills and was located in the town of Samastipur. The sugarmill was a major success and helped to boost the economy of Bihar.
The other options are incorrect. Option A, 1903, is incorrect because the Darbhanga Raj Sugar Mills was not set-up until 1905. Option C, 1910, is incorrect because the Darbhanga Raj Sugar Mills was already in operation by 1910. Option D, 1915, is incorrect because the Darbhanga Raj Sugar Mills was a major success by 1915.
The Darbhanga Raj Sugar Mills was a major success because it was well-managed and had access to a reliable source of sugarcane. The sugarmill also benefited from the fact that Bihar was a major producer of sugarcane. The sugarmill was able to produce high-quality sugar and sell it at a competitive price. This helped to boost the economy of Bihar and improve the lives of the people who lived there.