Concept: The fear of losing the Qur'an during Abu Bakr's caliphate led to its official collection into a single book.Explanation:When many companions who had memorised the Qur'an died in battle, there was a serious risk that parts of it would be lost.This happened during the caliphate of Abu Bakr (referred to as Abu Ilakr in the question).To preserve the complete text, Abu Bakr ordered Zayd ibn Thabit to gather all written and memorised verses together.The verses were then compiled into a single manuscript.So the main result of this fear was the compilation of the Qur'an.Answer: D. compilation