I did not choose any fast install option, as no such thing was offered. As I wrote, I told Avast! to update the program, which it did. It then asked me to restart the computer, which I did. Avast! then, for the second straight time of updating the program, proceeded to immediately install Chrome.
In short, no options offered, none chosen, Chrome installed without asking if I wanted it installed, just as I wrote in my first posting in this thread.
(Strictly as an aside, I'm not a beginner, having been using PCs since March 1983, on-line since October, 1983, so I have reason to believe that I know how to choose options when they are offered.)