Code: Select all
\documentclass[fleqn]{article}
\usepackage{amsmath}
\usepackage{multienum}
\usepackage{multicol}
\usepackage[shortlabels]{enumitem}
\usepackage{shortlst}
\usepackage[version=3]{mhchem}
\begin{document}
\begin{minipage}[t]{2.2in}
\begin{multienumerate}
\mitemxxx{\ce{^{56}_{27}\,Co}}{\ce{^{55}_{26}\,Fe}}{\text{none of these}}
\mitemxxo{\ce{^{57}_{25}\,Mn}}{\ce{^{58}_{24}\,Cr}}
\end{multienumerate}
\end{minipage}
\end{document}
