documentclass[10pt,a4paper,oneside]{book}
newcounter{questionnumber}
usepackage[brazil]{babel}
usepackage[usenames,dvipsnames]{xcolor}
%----------------------------------------------------
%Here is the answer key environment suggested by another forum.
%It stores the answers by the command answer{}, which allocates
%an organized list of answers at the end of the document,
%by the using of showanswers command.

usepackage{xparse}
ExplSyntaxOn

% first of all we define the user level commands
NewDocumentCommand{answer}{ m }{ malmedal_input_add:n { #1 } }
NewDocumentCommand{showanswers}{ }{ malmedal_output_direct: }

% allocate some variables:
% 1. a sequence for global storage of the inputs;
% 2. a temporary sequence when we need to reverse;
% 3. a counter (integer variable)
seq_new:N g_malmedal_input_seq
seq_new:N l_malmedal_temp_seq
int_new:N l_malmedal_count_int

% store globally an input in the sequence
cs_new:Npn malmedal_input_add:n #1
 {
  seq_gput_right:Nn g_malmedal_input_seq { #1 }
 }

% how to output in direct order; we simply do a mapping function calling
% malmedal_print:n after incrementing the counter
cs_new_protected:Npn malmedal_output_direct:
 {
  int_zero:N l_malmedal_count_int
  seq_map_inline:Nn g_malmedal_input_seq
   {
    int_incr:N l_malmedal_count_int
    malmedal_print:n { ##1 }
   }
 }

% the printing macro; change here for adapting to your wishes
cs_new:Npn malmedal_print:n #1
 {
  textcolor{RoyalBlue}{textbf{Question} ~ bfseriesint_to_arabic:n { l_malmedal_count_int }} ~ : ~ #1 par
 }
ExplSyntaxOff

%----------------------------------------------------
%Here I've built the question and the alternatives environment.

newcommand{makequestion}[2]{refstepcounter{questionnumber}parvspace{1em}noindenttextbf{(#1hspace{0mm}-hspace{0mm}textbf{#2})hspace{1mm}Questionhspace{0.3em}thequestionnumber.}\vspace{-4mm}ignorespaces}
newcounter{lettercounter}[questionnumber]
newcommand{alternative}{(alph{lettercounter})}
newenvironment{options}{begin{list}{alternative}{usecounter{lettercounter}}}{end{list}}
%----------------------------------------------------
%Here I've built the itens environment

newcounter{itemcounter}[questionnumber]
newcommand{newitem}{alph{itemcounter})}
newenvironment{itens}{begin{list}{newitem}{usecounter{itemcounter}}}{end{list}}


begin{document}

makequestion{MIT}{2014}
answer{A}

What do you think about life?

begin{options}
item I think it's a word.
item I think it's not a word.
end{options}

makequestion{MIT}{2011}
answer{B}

Is it a boy or a girl?

begin{options}
item A boy
item Yes.
end{options}

makequestion{MIT}{2013}
answer{How can I improve my code for a) and b) itens answers to be recognized and appear here, in the Answer Key?}

Answer the itens below:

begin{itens}
item Is $2>1$?
item Is $3<2$?
end{itens}

showanswers
end{document}