Concept:The compilation of Hadith refers to the official writing and collection of the sayings, actions, and approvals of Prophet Muhammad (peace be upon him).
Explanation:During the lifetime of the Prophet and the period of the Caliphs, Hadith were mostly preserved through memory and oral transmission.
The formal, organised compilation of Hadith into written collections began under the instruction of the Umayyad Caliph, Umar bn Abdul Aziz.
He ordered the learned scholars of his time to gather and write down authentic Hadith so that knowledge would not be lost.
Thus, the compilation process is historically credited to Umar bn Abdul Aziz, not to Abdullahi bn Umar or Umar bn Kattab.
Answer:B. Umar bn Abdul Aziz.