Which is the main source of irrigation for the cropped area of Rajasthan?

The correct answer is B, wells and tube wells. Although the Indira Gandhi Canal is the most celebrated irrigation work in Rajasthan, canal command covers only a part of the state, mainly the north-west and the Chambal and Mahi tracts. Across the rest of the state farmers depend on groundwater drawn from open wells and tube wells, which together water the largest share of the irrigated area. The consequence is a steadily falling water table and a long list of over exploited blocks, which is the standard follow up question.

Option A, tanks and ponds, matter in the south and south-east, in Udaipur, Bhilwara and Banswara, but they serve a small share. Option C, direct lift from rivers, is limited because most Rajasthan rivers are seasonal and the Chambal flows in a deep gorge. Option D, springs, is negligible in a state with little high rainfall terrain. Read the question as asking for the largest share and groundwater is the answer.