Yes very true but here motto was to ask which keywords are meant file handles and answer would be STDIN, STDOUT, STDERR
Then please write STDIN, STDOUT, STDERR. I thought you did mean a, b and c.
And a, b, c are also valid file handles:
$ perl -wE 'use strict; open a, "<", "TODO"; say <a>'
It is also slightly annoying to have several correct answers within a poll; the question which of several correct answers is more correct doesn't make sense, if you start thinking about it.
Thanks for the quiz anyway.