Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R). Assertion (A): Balban made his government firm and centralised all authority in his hands. Reason (R): He wanted to protect the north- west frontier against Mongol invasions. Select the correct answer from the codes given below:

- Balban (Ghiyas ud din Balban), Sultan of Delhi (1266-1287), faced significant internal challenges (power of nobles, weak administration after Iltutmish) and external threats (Mongols). - He adopted a policy of "Blood and Iron" to strengthen his rule, crushing internal rebellions and asserting the supremacy of the Sultan. - He disbanded the Corps of Forty (Chahalgani) nobles who had become powerful. - He organized a strong army and established a robust espionage system. - He gave high priority to the defence of the north-west frontier against the recurring Mongol invasions, fortifying strategically important locations and deploying his best generals there. - The necessity of consolidating resources and power to effectively counter the formidable Mongol threat was a primary driver for his centralizing policies.