user: Given the task definition, example input & output, solve the new input case.
You are given a paragraph, a question and some answer options (associated with "A", "B", "C", "D", etc.) You need to list all the correct answer options with their associated letters (e.g. "A" can be a valid answer). Note that sometimes, more than one option can answer the question correctly and completely. In those cases, please generate all such options separated by a comma (e.g. "A, B" is a valid answer). Do not generate anything else apart from one or more of the following characters: 'A', 'B, 'C', 'D', etc.
Example: Paragraph- Sent 1: Obama was born on August 4, 1961, at Kapiʻolani Maternity & Gynecological Hospital in Honolulu, Hawaii.
Sent 2: He is the only President to have been born in Hawaii.
Sent 3: He was born to a white mother and a black father.
Sent 4: His mother, Ann Dunham (1942-1995), was born in Wichita, Kansas, of mostly English descent, with some German, Irish, Scottish, Swiss, and Welsh ancestry. Question: How old was Obama's mother when he was born? (A) teenager (B) in his 40s (C) mid 20s (D) almost twenty.
Output: D.
Obama was born in 1961. His mother was born in 1942 and 1961-1942=19. Therefore, "almost twenty" answers the question sufficiently.

New input case for you: Paragraph- Sent 1: Although  Bin Laden, Atef, and KSM initially contemplated using established al Qaeda members to execute the planes operation, the late 1999 arrival in Kandahar of four aspiring jihadists from Germany suddenly presented a more attractive alternative.
Sent 2: The Hamburg group shared the anti-U.S. fervor of the other candidates for the operation, but added the enormous advantages of fluency in English and familiarity with life in the West, based on years that each member of the group had spent living in Germany.
Sent 3: Not surprisingly, Mohamed Atta, Ramzi Binalshibh, Marwan al Shehhi, and Ziad Jarrah would all become key players in the 9/11 conspiracy.
Sent 4: Mohamed Atta was born on September 1, 1968, in Kafr el Sheikh, Egypt, to a middle-class family headed by his father, an attorney.
Sent 5: After graduating from Cairo University with a degree in architectural engineering in 1990, Atta worked as an urban planner in Cairo for a couple of years.
Sent 6: In the fall of 1991, he asked a German family he had met in Cairo to help him continue his education in Germany.
Sent 7: They suggested he come to Hamburg and invited him to live with them there, at least initially.
Sent 8: After completing a course in German, Atta traveled to Germany for the first time in July 1992.
Sent 9: He resided briefly in Stuttgart and then, in the fall of 1992, moved to Hamburg to live with his host family.
Sent 10: After enrolling at the University of Hamburg, he promptly transferred into the city engineering and planning course at the Technical University of Hamburg-Harburg, where he would remain registered as a student until the fall of 1999.
Sent 11: He appears to have applied himself fairly seriously to his studies (at least in comparison to his jihadist friends) and actually received his degree shortly before traveling to Afghanistan.
Sent 12: In school, Atta came across as very intelligent and reasonably pleasant, with an excellent command of the German language.
Sent 13: When Atta arrived in Germany, he appeared religious, but not fanatically so.
Sent 14: This would change, especially as his tendency to assert leadership became increasingly pronounced.
Sent 15: According to Binalshibh, as early as 1995 Atta sought to organize a Muslim student association in Hamburg.
Sent 16: In the fall of 1997, he joined a working group at the Quds mosque in Hamburg, a group designed to bridge the gap between Muslims and Christians.
Sent 17: Atta proved a poor bridge, however, because of his abrasive and increasingly dogmatic personality.
Sent 18: But among those who shared his beliefs, Atta stood out as a decisionmaker. 
Question: Were the key players in the 9/11 conspiracy who executed the plane operations established al Qaeda members? (A) Yes (B) Not specified.
Output:

assistant: A.