Concept:Caliph Uthman b. Affan is best remembered for making one official written copy of the Qur'an.Explanation:During his reign, different recitations of the Qur'an began to appear among Muslim communities.To prevent confusion, he ordered a committee to copy the original manuscript using the Quraysh dialect.He sent official copies to major provinces and ordered the removal of other personal copies.This action preserved the Qur'an's text and ensured one authentic standard version.Answer:A. Standardization of the Qur'an.