Definition: In this task you are given a list of triplets of the form [subject, predicate, object] and the output should be a question based on the triplets but with the subject and/or object replaced with blanks (represented using two or more consecutive underscores). Triplet values encompassed in [*] are special tokens that can be replaced with synonyms. The objective is to construct a question in a manner that (a) captures the facts specified in at least one of the triplets, and (b) ideally contains a limited number of blanks such that it is a well-formed question that is easy to answer. A blank can represent a single word or a phrase.
Input: [['William Anders', 'OCCUPATION', 'Fighter pilot'], ['William Anders', 'WAS_A_CREW_MEMBER_OF', 'Apollo 8'], ['Apollo 8', 'BACKUP_PILOT', 'Buzz Aldrin'], ['Apollo 8', 'CREW_MEMBERS', 'Frank Borman'], ['Apollo 8', 'OPERATOR', 'NASA'], ['William Anders', 'STATUS', '"Retired"']]

William Anders served as a fighter pilot and was a member of _____'s crew. He is now retired. Frank Borman was also a crew member of the NASA operated Apollo 8. Buzz Aldrin was a back up pilot for Apollo 8.