[Tex/LaTex] LaTeX gives error undefined control sequence table

Question

\documentclass[journal]{IEEEtran}
\hyphenation{Smart Grid}
\usepackage[classicReIm]{kpfonts}
\usepackage{siunitx,booktabs}
\usepackage{subfloat}
\usepackage{subcaption}
\usepackage{graphicx}
\usepackage{color} %for colors
\usepackage{epstopdf}
\usepackage{url}
\usepackage{hhline}%%%
\usepackage{float} %for fix the image position
%\usepackage[]{algorithm2e}
\usepackage{amsmath} %% for case bracket
%\usepackage{url}
\usepackage{multirow} %  for devide row
\usepackage{caption}
%\usepackage{subcaption} % forr subfigures
\usepackage{multicol}
%\usepackage{subfig}
%\usepackage{cite}
\usepackage{cleveref}
\usepackage{amsmath}
\pagenumbering{gobble} %%% for without page numbers
\usepackage{float}
%\usepackage{algorithm}
\usepackage{array}
\usepackage{pdflscape}
\usepackage[classicReIm]{kpfonts}
\begin{document}
\begin{table}[H]
\centering \small
\tablesize{\footnotesize}
\caption{Comprehension of recent and relevant work.} \label{litrature}
\begin{tabular}{C{2.5cm}C{6cm}C{2.5cm}C{2.5cm}}
\toprule
\centering{\bf Methodologies } & \centering{\bf Features}&\centering{\bf Targets Achieved}&\bf{Limitations and Remarks} \\
 \midrule
        %\hline Optimal power scheduling method for DR in HEMS is presented in \cite{9} & GA & Cost and PAR reduction & Increased system complexity \\
 MILP& Optimal domestic load scheduling \cite{35} & Electricity cost reduction & The cost is reduced at expense of user discomfort\\
      \midrule Greedy algorithm& Heuristic optimization of generic cost model \cite{6} & Reduced user frustration and electricity cost & The PAR is ignored and complexity of the system is increased \\

        \midrule GWO and ILP &GWO applied to economic load dispatch problems \cite{3}& Load dispatching in off-peak hours & Solved economic load dispatch (ELD) problems in the current study \\  \bottomrule
\end{tabular}
\end{table} 
\end{document} 

Answer 1

You need to define the C column. I took the definition from here.

\documentclass[journal]{IEEEtran}
\usepackage{siunitx,booktabs}
\usepackage{float} %for fix the image position
\usepackage{amsmath} %% for case bracket
\pagenumbering{gobble} %%% for without page numbers
\usepackage{float}
\usepackage{array}
\usepackage[classicReIm]{kpfonts}
% from https://tex.stackexchange.com/a/175138/121799
\newcolumntype{C}[1]{>{\centering\arraybackslash}m{#1}}
\begin{document}
\begin{table}[H]
\centering \small
\caption{Comprehension of recent and relevant work.} \label{litrature}
\begin{tabular}{C{2.5cm}C{6cm}C{2.5cm}C{2.5cm}}
\toprule
\textbf{Methodologies } & \textbf{Features}&\textbf{Targets Achieved}&\bf{Limitations and Remarks} \\
 \midrule
        %\hline Optimal power scheduling method for DR in HEMS is presented in \cite{9} & GA & Cost and PAR reduction & Increased system complexity \\
 MILP& Optimal domestic load scheduling \cite{35} & Electricity cost reduction & The cost is reduced at expense of user discomfort\\
 \midrule 
 Greedy algorithm& Heuristic optimization of generic cost model \cite{6} & Reduced user frustration and electricity cost & The PAR is ignored and complexity of the system is increased \\
 \midrule 
 GWO and ILP &GWO applied to economic load dispatch problems \cite{3}& Load dispatching in off-peak hours & Solved economic load dispatch (ELD) problems in the current study \\  \bottomrule
\end{tabular}
\end{table} 
\end{document}