what form are Microsoft Dynamics AX 2012 model files stored and shared?

Where and in what form are Microsoft Dynamics AX 2012 model files stored and shared?

A.
in a separate database as .aod and .ald files

B.
in the Microsoft Dynamics AX 2012 Microsoft SQL Server database, as .axmodel files

C.
in a separate Microsoft SQL Server database as a model store, with the .axmodel files imported
from the application file share

D.
in the Microsoft Dynamics AX Microsoft SQL Server database as a model store, with the .axmodel
files in a shared network folder location