Assertion (S) In Rajasthan, sand is spreading towards the north - eastern plains. Reason (R) There exist 12 gaps in the Aravalli ranges in the middle of Jhunjhunu district in Ajmer.

• A. Both S and R are correct R is the correct explanation of S.
• B. S and R both are correct R is not the explanation of S
• C. S is correct but R is wrong.
• D. S is wrong but R is correct.