Given below are Two statements one labelled as Assertion (A) and the other as Reason (R): Assertion (A): Balban made his government firm stable and centralized all authority in his hands; Reason (R): He wanted to protect North-West frontier against Mongol invasions.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A)
• B. Both (A) and (R)are true, but (R) is not the correct explanation of (A)
• C. (A) is true, but (R) is false
• D. (A) is false, but (R) is true.