= Solution
\b[This is a <C-centered orthorhombic lattice>.] The translation $(1/2,1/2,0)$ takes each A molecule to another A molecule and each B molecule to another B molecule. Thus the conventional cell has two <lattice points>.
A two-molecule <crystal motif> can be chosen as A at $(0,0,0)$ and B at $(1/2,0,1/2)$. Attaching that same motif to both C-centered <lattice points> produces all four molecules, hence \b[eight <iodine> atoms per conventional cell].
The centers alone appear face-centered, but $(1/2,0,1/2)$ exchanges A and B orientations. It is not a translation symmetry of the oriented molecular solid. An F-centered assignment would discard essential motif information.
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