Step 1: Understanding the Concept:
Angle of repose is the angle at which a pile of granular material becomes stable.
It is affected by various factors including moisture content.
Step 2: Key Formula or Approach:
No specific formula.
Need to understand the relationship between moisture content and angle of repose.
Step 3: Detailed Explanation:
Angle of repose of grains changes with moisture content.
Higher moisture content generally increases the angle of repose.
Moisture content also affects the linear dimensions of grains due to swelling.
Both statements are correct.
However, the change in angle of repose is due to increased cohesion and adhesion between grains, not primarily due to changes in linear dimensions.
Thus, both A and R are true, but R is not the correct explanation of A.
Step 4: Final Answer:
Both A and R are true but R is NOT the correct explanation of A.
Hence, the correct option is (B).