The correct answer is D. Sitamarhi.
Jamui, Arwal, and Bhojpur are all highly irrigated districts of Bihar. Sitamarhi, on the other hand, is not a highly irrigated district. In fact, it is one of the least irrigated districts in the state.
According to the 2011 census, only 22.5% of the land in Sitamarhi is irrigated. This is significantly lower than the state average of 43.5%. The low level of irrigation in Sitamarhi is due to a number of factors, including the lack of water resources, the poor condition of irrigation infrastructure, and the low level of investment in irrigation.
The lack of water resources is a major problem in Sitamarhi. The district receives an average annual rainfall of only 1,000 mm. This is significantly lower than the state average of 1,200 mm. The low rainfall means that there is a limited amount of water available for irrigation.
The poor condition of irrigation infrastructure is another major problem in Sitamarhi. The district has a large number of old and dilapidated irrigation canals. These canals are often blocked with silt and debris. This makes it difficult to irrigate the land.
The low level of investment in irrigation is also a major problem in Sitamarhi. The state government has not invested enough money in irrigation in the district. This has led to a decline in the level of irrigation in the district.
The low level of irrigation in Sitamarhi has a number of negative consequences. It leads to low agricultural productivity, low incomes for farmers, and rural poverty. It also contributes to environmental problems, such as deforestation and soil erosion.
The government needs to take steps to improve the level of irrigation in Sitamarhi. This can be done by increasing the investment in irrigation, improving the condition of irrigation infrastructure, and promoting the use of modern irrigation techniques.