As you can see with the red arrows I do not have perfect squares and I think that all this depends on the letter used. But is it possible to find a solution to not use tabular?
There is also another problem. Should I use aligned or other strategies to get a perfect alignment in mathematical mode? In which way could I have an optimal result?
\documentclass[leqno,11pt,landscape,a3paper]{extarticle}
\renewcommand*\sfdefault{uop}
\renewcommand*\familydefault{\sfdefault} %% Only if the base font of the document is to be sans serif
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\showhyphens{matematica}
\usepackage[italian]{babel}
\showhyphens{matematica}
\usepackage{geometry}
\geometry{%
tmargin=0.7in,
bmargin=0.4in,
lmargin=0.3in,
rmargin=0.3in
}
\usepackage{graphicx,multicol,amsmath,amssymb}
\graphicspath{ {img/} }
\usepackage{fancyhdr}
\pagestyle{fancy}
\setlength{\headheight}{17pt}
\lhead{\sffamily\bfseries Classroom \textit{School}}
\chead{\sffamily\bfseries a.s. 2018--2019}
\rhead{\sffamily\bfseries Test
--- FISICA --- Fila 1}
\usepackage[italic,basic, defaultmathsizes]{mathastext}
\MTlettershape{sl}\Mathastext
\usepackage{titlesecmathtools}
\usepackage\usepackage[T1]{calrsfsfontenc}
\DeclareMathAlphabet{\pazocal}{OMS}{zplm}{m}\usepackage[utf8]{ninputenc}
\begin{document}
\begin{multicols}{1}
\begin{enumerate}
\item La velocità di 1,00$\cdot 10^2$ m/s espressa in km/h è:\\
$\fbox{A}$ 36 km/h.\\
$\fbox{B}$ 360 km/h.\\
$\fbox{C}$ 27,8 km/h.\\
$\fbox{D}$ $3,\!60\cdot 10^{8}$ km/h.\\
$\fbox{E}$ \begin{tabular}{lllllllllllll}
\multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{6}{c}{} \\
\hline
\end{tabular}
\item In fisica nucleare si usa l'angstrom (simbolo: 1\AA=$10^{-10}$ m) e il fermi o femtometro (1 fm= $10^{-15}$ m). Qual è la relazione tra queste due unità di misura?\\
$\fbox{A}$ 1 \AA = $10^5$ fm.\\
$\fbox{B}$ 1 \AA = $10^{-5}$ fm.\\
$\fbox{C}$ 1 \AA = $10^{-15}$ fm.\\
$\fbox{D}$ 1 \AA = $10^{3}$ fm.\\
$\fbox{E}$ \begin{tabular}{lllllllllllll}
\multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{6}{c}{} \\
\hline
\end{tabular}
\end{enumerate}
\end{multicols}
\clearpage
\end{document}