Concept:The fear that the Qur'an might be lost during the caliphate of Abu Bakr led to its compilation into a single written text.Explanation:After the Battle of Yamama, many companions who had memorised the Qur'an were martyred.This made Umar ibn al-Khattab fear that the Qur'an could be completely lost.He therefore advised Caliph Abu Bakr to compile the Qur'an in written form.Abu Bakr accepted the advice and formed a committee headed by Zayd ibn Thabit.The committee collected the verses and compiled them into one manuscript.This preserved the Qur'an for future generations.Answer:D. compilation