A simple semi-manual solution could be search and replace the fixed string as "COD:" at the beginning of the line, to adapt these strings to something that can be understood by a LaTeX converter/generator.
There are several tools for the second step and probably hundreds for the first, so I will just expose one way that I know in Linux, but with little imagination can be adapted in many ways to other tools and operative systems.
First step: Seearch & replace "COD:","\nA ", \nB ", etc. with gedit or any other tool, but preferably with one that can find end of lines (\n) and tabulations (\n), to left the text with this format:
* COD: 7
¿A qué número de revoluciones se alcanza la potencia máxima de un motor?
^^ Al número de revoluciones a las que gira el motor en el momento de arrancarlo.
++ A bajas revoluciones.
++ A un número intermedio de revoluciones.
++ A un número de revoluciones próximo al máximo.
N:RESPUESTA: D
N:NORMA: Sin referencia
Second step: Convert to LaTeX with SDF (available in official packages at least in Debian and Ubuntu distributions).
$ sdf +sdf2latex_ yourfile.txt
The ouput is a yourlife.tex but without preamble and document class, so you must include at least:
\documentclass[spanish]{article}
\usepackage{babel}
\usepackage[utf8]{inputenc} % problems? try latin9
The raw ouput is:
%%% This file was generated using SDF $version by
%%% Ian Clatworthy (ianc@mincom.com) and the 2latex_ driver
%%% $Id: tolatex.pl,v 1.1.1.2 1998/03/22 09:39:20 valerio Exp valerio $
%%% written by Valerio Aimale <valerio@svpop.com.dist.unige.it>.
%%% SDF is freely available from http://www.mincom.com/mtr/sdf
\begin{document}
\begin{itemize} % Level 1
\item COD: 7 ¿A qué número de
revoluciones se alcanza la potencia máxima de un motor?
\begin{enumerate} % Level 2
\item Al número de revoluciones a las que
gira el motor en el momento de arrancarlo.
\item A bajas revoluciones.
\item A un número intermedio de revoluciones.
\item A un número de revoluciones próximo al máximo.
\end{enumerate}
\end{itemize}
RESPUESTA: D
NORMA: Sin referencia
\end{document}
After adding the preamble, you can compile to obtain this result:

This is not exactly as your example, because there are not a description environments but itemize. As far I know SDF manage only unordered or numbered list, but change this is a simple search and replace in all the document.
The manual part could be enclose with [ ] "COD:7" and mark in bold font the correct answer, but with a editor with macro language as Nedit it could be easily automatized in five setps. If you do not have a good editor, see this comparative.