B. Unlike APPLICATION variables, SERVER variables are always available and may always be used. This cannot be prevented.
A2:
A. All of the other options are incorrect.
A3:
E. This is a trick question. There is no onServerStart() method, if there was that would be the place to set SERVER variables. And while onApplicationStart(), onRequestStart(), and onRequest() could indeed be used to set SERVER variables, so could any other files and code too, and there is no special reason that these should be used.