documentclass{article}
usepackage{amsmath}
usepackage{etoolbox}
usepackage{xparse}
usepackage{pgffor}

makeatletter

defae@tmp@frontmatter{}
defae@list{}
NewDocumentCommandqchoice{ mom }
  {%%
    defae@tmp@frontmatter{#2}
    letae@listrelax
    foreach myn in {#3}
    {%%
      ifxae@listrelax
        xdefae@list{noexpand#1{expandonceae@tmp@frontmatterexpandoncemyn}}%%
      else
        xdefae@list{expandonceae@listnoexpandpar%%
                     noexpand#1{expandonceae@tmp@frontmatterexpandoncemyn}}%%
      fi
    }%%
    ae@list}

makeatother

newcommandaebf[1]{$rightarrow$ textbf{#1} DONE}
pagestyle{empty}
begin{document}

qchoiceaebf[front matter::]{a,b,c,d}

end{document}

documentclass{article}
usepackage{amsmath}
usepackage{xparse}

ExplSyntaxOn

tl_new:N  l_qchoice_command_sequence_tl
tl_new:N  l_qchoice_front_matter_tl
tl_new:N  l_qchoice_csv_choices_tl
tl_new:N  l_qchoice_tmp_tl
seq_new:N l_qchoice_choices_seq

NewDocumentCommandqchoice{ mom }
  {%%
    tl_set:Nn  l_qchoice_command_sequence_tl {#1}
    tl_clear:N l_qchoice_front_matter_tl
    tl_clear:N l_qchoice_csv_choices_tl
    IfNoValueF{#2}
      {
        tl_set:Nn l_qchoice_front_matter_tl {#2}
      }
    seq_set_split:Nnn   l_qchoice_choices_seq {,} {#3}
    seq_map_function:NN l_qchoice_choices_seq qchoice_parse_choices:n
    l_qchoice_csv_choices_tl
  }

cs_new:Npn qchoice_parse_choices:n #1
  {
    tl_clear:N      l_qchoice_tmp_tl
    tl_set:No       l_qchoice_tmp_tl l_qchoice_front_matter_tl
    tl_put_right:Nn l_qchoice_tmp_tl {#1}
    tl_set:No       l_qchoice_tmp_tl {{l_qchoice_tmp_tl}}
    tl_if_empty:NTF l_qchoice_csv_choices_tl
      {
        tl_set:No        l_qchoice_csv_choices_tl l_qchoice_tmp_tl
      }
      {
        tl_put_right:Nn  l_qchoice_csv_choices_tl {par}
        tl_put_right:No  l_qchoice_csv_choices_tl {l_qchoice_tmp_tl}
      }
  }

ExplSyntaxOff

newcommandaebf[1]{$rightarrow$ textbf{#1} DONE}
pagestyle{empty}
begin{document}

qchoiceaebf[front matter::]{a,b,c,d}

end{document}

tl_set:No       l_qchoice_tmp_tl {{l_qchoice_tmp_tl}}