Instructions: 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: What was the site of the successful military operation Ji staged against a co-regent? Passage:Jiang Ji (died 18 May 249), courtesy name Zitong, was an official and military general of the state of Cao Wei during the Three Kingdoms period of China. Born in the late Eastern Han dynasty, Jiang Ji started his career as a low-level official in his native Yang Province before becoming a subordinate of Cao Cao, the warlord who controlled the central government towards the end of the Eastern Han dynasty. After the end of the Eastern Han dynasty, he served in the state of Cao Wei through the reigns of the first three emperors – Cao Pi, Cao Rui and Cao Fang – and held various appointments in the military before rising to Grand Commandant, one of the top positions in the central government. During his service in Wei, he was known for being candid in giving advice to the emperor on various issues, including consolidating power, halting labour-intensive construction projects, and officials' abuses of power. In February 249, he joined the regent Sima Yi in staging a successful coup d'état against his co-regent Cao Shuang, but died from illness a few months later.
 Links: a. Cao Shuang b. Coup d'état c. Sima Yi d. Cao Wei
Output:
b