I don't really know but I believe that (C) is wrong because the navigation database in the permanent navigation database is not modified. Instead, new data is added to the temporary or supplemental database.
I have no idea about (A). My best guess is that crew entered data can only be entered by certain pages but certainly not any time. And reading data is not possible as well any time e.g. when monitoring the IRS system via FMC pages. Just a guess ...
EoD