Option a is the correct answer. Alauddin Khalji initiated the concept of a 'Public Distribution System' during medieval India. Alauddin Khalji's reign saw significant economic reforms, including the establishment of a centralized grain market (Mandi) and regulations to control prices. These measures aimed to ensure food availability and stabilize prices for the public, resembling the essence of a modern public distribution system, although it differed in its specific structure and scope.