\RequirePackage{xkeyval}

\def\@paper{}
\DeclareOptionX{a4paper}{\edef\@paper{\@paper Read `a4paper` option as #1. }}

\def\@hello{Missing `hello' parameter. }
\DeclareOptionX{hello}{\edef\@hello{Defined `hello' to #1. }}

\ProcessOptionsX*

\providecommand{\scenario}{%
  \@paper%
  \@hello%
}