Step 1: Understanding irrigation sources.
Among different sources, tubewells are easy to construct, low-cost, and widely used for irrigation, especially in Indo-Gangetic plains.
Step 2: Analyze other sources.
(B) Pond – traditional, but limited water storage capacity.
(C) Canal – requires large investment, not easily accessible to all farmers.
(D) Tap – domestic water supply, not a major irrigation source.
Step 3: Conclusion.
Hence, the easiest and cheapest irrigation source is Tubewell.