'The Forty' (Turkish: Chihalgani) referred to the powerful group of 40 Turkish nobles who controlled the Sultanate during the period of political instability after Iltutmish. They assassinated Sultan Nasir-ud-din Mahmud and eventually placed Balban on the throne, who later ruthlessly suppressed them to consolidate power. Note the option has a typo: 'thiefs' should be 'thieves'.