The historical database is specifically where information on prior projects - including events such as a project being terminated - would reside. This answer is specific and thus a better response than "project closing documents" even though the historical database may have been updated in the project closure phase (and, most likely was done at this time for the project since it was terminated!).
I was doing a test yesterday on prepcast and this question is one tough cookie.
The question asks where we'd go to learn about the reason a project was terminated. I chose Project of Phase Closure Documents but the correct answer was Historical Database. I read PMBOK pg 104 and everything still leads me to Project Closure Documents (which I assume is a subset of the Historical Database).
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