These are the vital questions that arise in the mind of a person when he looks upon the religions for a critical study. So, which religion is the right one and how can the seeker of truth know it? This is the subject of this booklet. Publisher's Note As our Prophet Muhammad had said that every child is born on its nature, it is his parents that make him a Jew or a Christian, we observe that the followers of different faiths use to consider their own faith to be the most true one in comparison to other faiths. In fact, the matter of adopting a religion is a birthright of every person, and when someone attains the age of understanding, he should look into the matter of his religion. As there are many religions in the world and each claiming to be the only true one, some have a greater number of followers than others that are not so widespread. It is in the interest of each person to make a comparative study of religions and choose for himself the best he has found. Similarly, he should also check his religion as regards the misconceptions that took their place in every religion. Keeping the religion pure and safe from all types of additions and changes is also a person's duty for his own sake. In this book, the author has discussed some vital questions that arise in the mind of a person when he looks upon the religions for a critical study: Is it necessary to adopt a religion? What is the criteria to judge a religion? How to differentiate between a false and a true religion? How to check the pure teachings of a religion against the additions that took place by the passage of time and by the misbehavior of irresponsible clerics and the so-called scholars?... and likewise. We hope that this book will help a lot to a person who gives serious attention to a matter such as religion, and he must do so because religion is a matter that should be given serious attention. In the end all praise is due to Allah, and upon Him we depend.