Concept:The logical sequence of sentences should build a cause-and-effect explanation for the need of irrigation in Indian agriculture.Explanation:Sentence R states the primary cause: irrigation is needed due to spatio-temporal variability in rainfall.Sentence P then describes the consequence: large tracts are deficient in rainfall and drought-prone.Sentence S identifies the specific regions: North-Western India and Deccan Plateau.Sentence Q concludes by noting that winter and summer are dry in most parts, reinforcing the need for irrigation.Thus, the correct order is R → P → S → Q.Answer:RPSQ (Option A)