Which of the following religions has the smallest number of adherents world-wide?

Judaism has the smallest number of adherents worldwide compared to the other religions listed. Estimates suggest that there are approximately 14 to 15 million Jews globally, which is significantly lower than the populations of Islam, Hinduism, and Buddhism. Islam, with over 1.9 billion followers, is one of the largest religions in the world. Hinduism also has a substantial following, with over 1.2 billion adherents, primarily in India and Nepal. Buddhism, while smaller than the first two, still boasts around half a billion followers globally. These population figures highlight the relatively small size of the Jewish community in comparison to the larger religious traditions, clarifying why Judaism is the correct answer in this context.