The chapters in the book have been divided into the following parts: (a) Introduction: It Introduces you to the topic of the chapter It also tells you what you Will leam tllrough the various topics covered m the chapter. (b) Sessions: It contains relevant Information on the session headings. The knowledge developed through sessions will enable you to perform certain activities. (c) Self Assessments: At the end of all topics under a session heading, Self assessment is Included to evaluate the knowledge of the leamers_ It compnses Multiple Choice Questions, Answer the following questions and Activity zone. (d) Exercises: At the end of each chapter, Exercises are Included to test the understanding of the matter read over the various topics. This section consists of Multiple Choice Questions, Fill m the blanks, State tme or false, Answer the following questions, Application based questions and Activity area We hope that this book will meet the needs and requirements of the students and teachers as laid down in tile syllabus. Any suggestion for ?uther improvement of the book Willbe most welcomed.