3This book has been written in accordance with the latest syllabus prescribed by the central board of secondary education, Delhi for secondary education (C.B.S.E) examination. The present book will help you to self-understand the subject in a better way. Unique features of this book 1.Written in very simple, easy to understand student friendly language. 2.The answer is written in a comprehensive style in most cases with well-illustrated and labeled diagrams where ever it was required. 3.All chapters of science book are covered. 4.All questions are made at par with CBSE question standard. 5.Every question has four options and they are very informative though only one will be the correct answer. 6.All questions are answered at last of each chapter. 7.Every answer is explained in detail. 8.Other than correct answer all other options are also discussed to understand why they are not the correct option for that question. 9.About 1200 Q & A. I hope this book will prove very useful to the students and teachers. Suggestions and constructive criticism for the further improvement of the book would be gratefully acknowledged and should incorporate in coming editions.