The correct answer is: b) Tubewells.
Tubewells are the primary source of irrigation in Bihar, accounting for over 60% of the state’s irrigation water. This is due to a number of factors, including the state’s relatively dry climate, the low cost of tubewell irrigation, and the government’s efforts to promote tubewell development.
Canals are the second most important source of irrigation in Bihar, accounting for about 20% of the state’s irrigation water. However, canals are not as reliable as tubewells, as they are often subject to water shortages.
Rainfall is the third most important source of irrigation in Bihar, accounting for about 15% of the state’s irrigation water. However, rainfall is highly variable, and can lead to floods or droughts.
Tanks and ponds are the least important source of irrigation in Bihar, accounting for only about 5% of the state’s irrigation water. This is because tanks and ponds are often small and shallow, and they can dry up during the dry season.
In conclusion, tubewells are the primary source of irrigation in Bihar, accounting for over 60% of the state’s irrigation water. This is due to a number of factors, including the state’s relatively dry climate, the low cost of tubewell irrigation, and the government’s efforts to promote tubewell development.