Correct Answer - D
Anhydrous beryllium halides are best prepared by the best route for the preparation of `BeF_(2)`. The compound itself is made as follows
`BeO+NH_(4)Fto(NH_(4))_(2)[BeF_(4)]`
or `BeO+2NH_(3)+4HFto(NH_(4))_(2)[BeF_(4)]`
Reaction with `C Cl_(4)` is a standard method for making anhydrous chlorides which cannot be obtained by dehydrating hydrates.