This is the thoroughly revised, updated, and enlarged edition of the book. This book has its origin in the analysis of the questions being asked in the examinations conducted by ASRB for ARS, ICAR-JRF/ SRF/NET, UGCNET, SAUs/CATET, UPSC, PCS, ICMR, CSIR, NAARM, DBT, NDRI, IARI/IVRI, JNU, BHU, Thsti and various agricultural universities.