(4) Where any land, in respect of which exemption has been granted under sub- section (1) or sub- section (2) or sub- section (3), ceases to be used, or is not within the prescribed time used, for the purpose for which exemption had been granted, the Administrator may, after giving the persons affected an opportunity of being heard withdraw such exemption. CHAP PREVENTION OF FRAGMENTATION CHAPTER XIV.- PREVENTION OF FRAGMENTATION