Hi Steve. Good question. Looking at the linked documentation, it seems that there is a slight syntax correction needed in your explanation of the answer. The "FREE" should be in parenthesis, not the DLL name, as in:
DBCC <dllname> ( FREE ) [ WITH NO_INFOMSGS ]
Example from the doc:
DBCC xp_sample (FREE);
I would suggest changing the answer option from "DBCC FREE" to "DBCC <dllname> (FREE)".