289.

Which is the most appropriate place to install a Strong-Named assembly that is intended for use among several web applications?

You would install a Strong-Named assembly in the Global Assembly Cache of the Web Server. It would not work for the Strong-Named assembly to be installed on a PDC server, unless that were, also, the web server. The solution's /bin directory or the virtual directory would not be places to install a Strong-Named assembly that is to be shared among several web applications.