Definition: In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
Input: Question: Who led the Great Turkish Invasion? Passage:The fortress was mentioned in The Georgian Chronicles, but the time of its construction is uknown. In the 1060s King Bagrat IV took it over from emir Fadlon. During the "Great Turkish Invasion" (1080) the fortress was captured by the enemy, and that is when it received the name "Kor Ogli". This name was still used on Soviet topographic maps. In July 1118, David the Builder besieged Agarani in one day, and in 1123 gave it to Ivane Orbeli. The Orbelis later rebelled against the King Georgy III, and lost their possession. "Agarani Fortress" was a summer residence of Georgian kings. According the chronicles, Queen Tamar was brought ill to Agarani and here she died, but her burial place is unknown. From 15th century the fortress belonged to Sologashvili family, when it was called "Kojori Fortress". According to Vakhushti Batonishvili, it was previously known as the "Azulula Fortress". In February 1921, the Georgian cadets of Officer School died in a battle against the Red Army, which happened by the fortress.
 Links: a. Great Turkish Invasion b. Great Turkish Invasion c. The Georgian Chronicles d. The Georgian Chronicles
Output:
a