\resheading in two column book document class

I managed to get sheading tab, but still there are some problems.

1. A black box with question number in white.
2. Insert indent of 1 cm for text throughout the document.
3. Can we define globally for spacing between items or there is the only way to put '\\'.

Here is the code for your kind reference,

\documentclass{book}
\usepackage{multicol}
\setlength{\columnsep}{1cm}
\usepackage[top=0.75in, bottom=0.75in, left=0.55in, right=0.85in]{geometry}
\usepackage{color}
\definecolor{mygrey}{gray}{0.75}
\textheight=9.75in
\raggedbottom
\setlength{\tabcolsep}{0in}
\newcommand{\isep}{-2 pt}
\newcommand{\lsep}{-0.5cm}
\newcommand{\psep}{-0.6cm}
\renewcommand{\labelitemii}{$\circ$}
%-----------------------------------------------------------
%Custom commands
\newcommand{\resitem}[1]{\item #1 \vspace{-2pt}}
{1\linewidth}{\textbf{#1 \vphantom{p\^{E}}}}\end{minipage}}}}
\begin{tabular*}{6.62in}{l @{\extracolsep{\fill}} r}
\textsc{{\textbf{#1}}} & \textsc{\textit{[#2]}} \\
\end{tabular*}\vspace{-8pt}}
%-----------------------------------------------------------
\begin{document}
\chapter{Exponents 1}
\begin{multicols}{2}
%%%% Start Question 1
$$\sqrt{9x^2}$$
If $x>0$, which of the following is equivalent to the given expression?\\
\\
\begin{enumerate}
\item[A)]   3x\\
\item[B)]  $3x^2$\\
\item[C)]  18x\\
\item[D)]  $18x^4$\\
\end{enumerate}
%%%% End Question 1
\end{multicols}
\end{document}


• Please do not only add an image, describe in words what the problem is. And please add a short compilable code to the question, do not force people to go to a web side they need to register ... – Kurt Mar 6 at 14:24
• Crosspost latex.org/forum/… – Johannes_B Mar 8 at 9:11