Problem with vertical space in enumerate environment

Question

I have a problem regarding the vertical space between \item and an image. I use the following code and the image doesn't move vertical as it should. Why is that? And how can I fix it?

\documentclass[12pt]{article}

\usepackage{graphicx}

\begin{document}

\begin{enumerate}
\item

\begin{enumerate}
\item

\vspace{0.3cm}

\includegraphics[scale=0.7]{2.2.a.png}

\end{enumerate}

\end{enumerate}

\end{document}

Edit I: Also I had deleted by mistake the \usepackage{graphicx} and it still compiled without error! How is that possible and why?

Answer 1

\documentclass[12pt]{article}

\usepackage{adjustbox}
\begin{document}

\begin{enumerate}
\item

\begin{enumerate}
\item


\adjustbox{valign=t}{\rule{1cm}{2cm}}

\end{enumerate}

\end{enumerate}

\end{document}