How to create invisible item in Beamer Overlays case by case?

Question

Please allow me to explain my situation. I am using Beamer overlay for a quiz. (And I love the pdf output). So, I give the students multiple choices on first slide. And next slide they get the answer. But, I want to add an additional comment after the answer, to describe little more about the topic. Here is what I have.

\begin{frame}{Programming Basics}
\texttt{Comments are followed by \underline{\hspace{2cm}}}
\begin{enumerate}
    \item<1> !
    \item<1> @
    \item<1> ::
    \item<1-2> ;
    \item<2> Only show this in second slide, ; I am comment
\end{enumerate}
\end{frame}

I like \setbeamercovered{transparent} so I don’t want to set to invisible. I just want the last item to show up after the answer, without a grey transparent item showing up on first slide, because this can give them a hint!!! (See the attached image)

I did some research but could not find the answer. Thank you.

Answer 1

\invisible is your new friend

\documentclass{beamer}
\setbeamercovered{transparent}
\begin{document}
\begin{frame}{Programming Basics}
    \texttt{Comments are followed by \underline{\hspace{2cm}}}
    \begin{enumerate}
        \item<1> !
        \item<1> @
        \item<1> ::
        \item<1-2> ;
        \invisible<1>{\item Only show this in second slide, ; I am comment}
    \end{enumerate}
\end{frame}
\end{document}