In the beginning, Turks practiced shamanism in Inner Asia. Their practice had cultic elements and emphasized Tengri (God), Umay (Fertility Goddess), Yer (Earth), and Su (Water). They believed in heaven and hell. During the first millennium CE, some small groups of Turks converted to Buddhism, Christianity, Judaism, or Zoroastrianism. Some Uighurs also converted to Manichaeism. However, as their westward movement accelerated in the tenth century CE, Turks became Muslims in large numbers and today Islam is the predominant religion in the Turkic world.The correct answer is D.