Option b is the correct answer. Statement 1 is incorrect: The first Mongol invasion of India took place in the reign of Sultan Shams-ud-din Iltutmish. Statement 2 is correct: Alauddin established a huge permanent, standing army to satisfy his ambition of conquest and to protect the country from Mongol invasion. The Mongols attacked at the worst time possible for Alauddin Khilji - when he was busy laying siege to Chittor. This time the Mongols travelled light. An army of 12,000 under Targhi's leadership moved to Delhi in a swift attack; many governors could not send their troops to Delhi in time. Alauddin Khilji was forced to retreat to Siri for about two months. The Mongols attacked and pillaged not only the surrounding areas, but Delhi itself. Alauddin Khilji continued to hold the fortress at Siri; Targhi withdrew the siege after a few months and left the area. Barani, a contemporary historian at that time, attributed this "marvel" to the prayers of the Sufi mystic Shaikh Nizamuddin Auliya. Statement 3 is incorrect: The next major Mongol invasion took place after the Khiljis had been replaced by the Tughlaq dynasty in the Sultanate. In 1327 the Chagatai Mongols under Tarmashirin, who had sent envoys to Delhi to negotiate peace the previous year, sacked the frontier towns of Lamghan and Multan and besieged Delhi. The Tughlaq ruler paid a large ransom to spare his Sultanate from further ravages. Muhammad bin Tughluq asked Ilkhan Abu Sa'id to form an alliance against Tarmashirin, who had invaded Khorasan, but an attack didn't materialize. Tarmashirin was a Buddhist who later converted to Islam. Religious tensions in the Chagatai Khanate were a divisive factor among the Mongols.