Missing $ Inserted error thrown in a custom command

This is my first post on this community. I am fairly new to latex and have added a custom function using newcommand. The command is as follows –

newcommand{addQuestion}[6]{
    textbf{#1}. #2
    begin{multicols}{2}
    begin{enumerate}[label=(alpha*)]
    item #3
    item #5
    item #4
    item #6
    end{enumerate}
    end{multicols}
}

and my document is as –

begin{document}
begin{multicols}{2}
addQuestion{Q27}{a sample question}{This}{That}{this}{that}
end{multicols}
end{document}

The Error is thrown on the line with addQuestion which says

xAssignment.tex.swp:23: Missing $ inserted.
<inserted text> 
                $
l.23 ...a sample question}{This}{That}{this}{that}

I did browse through the previous posts but found nothing helpful. Could anyone please help me with this.
TIA

documentclass{article}
usepackage{multicol}
usepackage{enumitem}
newcommand{addQuestion}[6]{
    textbf{#1}. #2
    begin{multicols}{2}
    begin{enumerate}[label=(alph*)]
    item #3
    item #5
    item #4
    item #6
    end{enumerate}
    end{multicols}
  }
begin{document}
addQuestion{Q27}{a sample question}{This}{That}{this}{that}
end{document}