(C) a-ii, b-iii, c-iv, d-i
Alluvial soil contains potash, phosphorus and lime (ii); Black soil is made from lava/Deccan trap, suitable for cotton (iii); Laterite soil has decreased humus in semi-arid environment (iv); Arid soil is sandy and saline (i).
Match each soil type with its most distinctive characteristic from the textbook. The key distinguisher for laterite is "humus poor in semi-arid environment" (not sandy/saline — that's arid). Arid = sandy + saline. Black soil = lava (Deccan trap) + cotton. Alluvial = potash, phosphoric acid, lime = fertile. Option C is the only one with all four correct pairs.