Why I get undefined control sequence with cline?

Question

I'm trying to make that table:

\documentclass[default]{sn-jnl}
\usepackage{verbatim}
\usepackage{hyperref}
\usepackage{graphicx}%
\usepackage{multirow}%
\usepackage{amsmath,amssymb,amsfonts}%
\usepackage{amsthm}%
\usepackage{mathrsfs}%
\usepackage[title]{appendix}%
\usepackage{xcolor}%
\usepackage{textcomp}%
\usepackage{manyfoot}%
\usepackage{booktabs}%
\usepackage{algorithm}%
\usepackage{algorithmicx}%
\usepackage{algpseudocode}%
\usepackage{listings}%
\usepackage{adjustbox}%
\theoremstyle{thmstyleone}%
\newtheorem{theorem}{Theorem}%
\newtheorem{proposition}[theorem]{Proposition}% 
\theoremstyle{thmstyletwo}%
\newtheorem{example}{Example}%
\newtheorem{remark}{Remark}%
\theoremstyle{thmstylethree}%
\newtheorem{definition}{Definition}%
\raggedbottom
\begin{document}
\title[Some title]{Some title}
\abstract{Some abstract}
\maketitle
\section{INTRODUCTION}
.....
\begin{table}[ht]
\centering
\caption{Statistical tests.\label{tab:II}}
\begin{adjustbox}{max width=1.0\textwidth,center}
\begin{tabular}{c c c c c c}
\hline
\multirow{5}{}{Algorithm} & \multirow{5}{}{No. of streams} \
\multicolumn{5}{l}{$\qquad \qquad  \qquad  \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad$ Inter-stream correlation} \[6pt]
\cline{3-6}
 &   & \multirow{2}{}{NIST} & \multirow{2}{}{Dieharder} & \multirow{2}{}{TestU01} & \multirow{2}{}{PractRand (bytes)} \[11pt]
\hline \
\textbf{A}  & $2^{127}$   & $>$ min. pass rate    &passed  & passed    & $>2^{43}$, $>2^{43}$  \[7pt]
\textbf{B} & $2^{63}$  & $>$ min. pass rate    &passed   & passed    & $>2^{43}$, $>2^{43}$  \[7pt]
\textbf{C}  & $2^{63}$ & $>$ min. pass rate    &passed   & passed    & $>2^{43}$, $>2^{43}$ \[7pt]
CG32    & $2^{31}$  & not applied    &not applied  & not applied    & $> 2^{43}$, $< 2^{34}$ \[7pt]
CG64-32   & $2^{31}$  & not applied    &not applied  & not applied    & $> 2^{43}$, $< 2^{35}$  \[7pt]
CG16    & $2^{15}$ & not applied    &not applied  & not applied    &$< 2^{24}$, $< 2^{17}$  \[7pt]
CG32-16  & $2^{15}$  & not applied    &not applied  & not applied  & $< 2^{20}$, $< 2^{18}$ \[7pt]
\hline
\end{tabular}
\end{adjustbox}
\end{table}%
\raggedbottom
\bibliography{cg-bibliography}
\end{document}

But I can't use cline, beacuse I get undefined control sequence. How to make that cline?

The full log:

! Undefined control sequence.
l.472 \cline
{3-6}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

Answer 1

The class is written quite horribly. If you don't have to use it, then use another one.

Anyway, the problem here is that it defines \toprule and \bottomrule similar to those of booktabs but... no idea what is supposed to happen after that. After these definitions you find

\let\cline\cmidrule

but the trouble is that at this point \cmidrule is not defined, and using it in the document will result in the error.

There are some workarounds but none will result in whatever the class is probably supposed to do.

1. You can load \RequirePackage{booktabs} before \documentclass. In this way you have a working \cline (which is the same as \cmidrule) but the class will overwrite the definition of \toprule and \bottomrule.
2. You can add \usepackage{booktabs}\let\cline\cmidrule in the preamble. Everything should then work, but the class' own definitions will be overwritten.
3. You can copy the original definition of \cline and restore it afterwards \let\LaTeXcline\cline\documentclass{sn-jnl}\let\cline\LaTeXcline. Then you'll have \cline and\cidrule doing different things.

I don't know which one's worse ;-)