AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
Option A is correct. Both A and R are true, and R is the correct explanation of A. Shifting cultivators move to fresh land precisely because continued cultivation decreases soil fertility.
Source: Primitive Subsistence Farming, Chapter 4
The passage directly states: "When the soil fertility decreases, the farmers shift and clear a fresh patch of land for cultivation." This confirms both the assertion and the reason, and establishes a direct causal link — making R the correct explanation of A. Choose A whenever the reason accurately and directly explains the assertion.