Solution:Sentence A will be the starting line as it introduces the main idea of the parajumble, i.e. the narrator met a gentleman who plays game with his grandchildren. And, Sentence D states that the gentleman picks names of some famous personalities from his generation.
So, D will follow A. Further, Sentence C states that the gentleman asks his grandchildren about those personalities & Sentence B states that the conversation starts between the narrator and the gentleman. So, B will follow C. Going through the options, option 'd' has the correct sequence,