Timur invaded India in 1398 during the nominal reign of Nasiruddin Muhammad Tughlaq, though actual power lay with his father, Sultan Mahmud Shah Tughlaq. The Tughlaq dynasty was already weak, making Delhi an easy target. Timur plundered the city brutally and returned with enormous wealth, leaving the Sultanate shattered. ANSWER: (A) Nasruddin Muhammad Tughlaq