You will be given a context, a subject and a relation. Your task is to generate a question based on the subject and relation. The generated question should include the given subject. Try to use a minimum number of words that are not present in either context, subject or relation while generating question.

Context : Boeing proposed a further-modified version of the missile, with improved guidance and longer range, however the MA-31 program went no further, and the last missiles in the U.S. Navy's inventory were expended in 2007.
Subject : MA-31
Relation : service entry
Which was the official year for the approval of MA-31?