The total capacity of a reservoir is 25 million cubic metres and dead storage is 5 million cubic metres. If the average volume of sediment deposition is 0.10 million cubic metre per year, then the usefulness of the reservoir will start reducing after A. 50 years B. 150 years C. 200 years D. 250 years

Option B is incorrect because the usefulness of the reservoir will start reducing after 50 years, not 150 years.

Option C is incorrect because the usefulness of the reservoir will start reducing after 50 years, not 200 years.

Option D is incorrect because the usefulness of the reservoir will start reducing after 50 years, not 250 years.