The present book has been designed and organized with the viewpoint to help the students to pinpoint the correct choice in a multiple choice question. In most of such cases two or more options may appear alike. This is where a clear concept and a sense of scientific logic make all the difference. In several questions there may be only a hairline difference. The questions in the book have been designed so as to develop the concept of the subject and scientific logic systematically. This helps the students in improving their scores. Tricks and blind answers may be disastrous and should not be practiced. Brief conceptual outlines of the concerned subject has been given followed by short answer type questions including previous GATE questions of the subject. Correct answer key has been provided at the end of each chapter.