a table displayed a few lines after where it should be

Question

Here is what I typed in the tex file:

This is some text that should appear just before the table. \begin{table} Table \end{table}

This is some text that should appear just after the table.

This is what displayed in the output:

This is some text that should appear just before the table. This is some text that should appear just after the table. Table

Here is the MWE:

\documentclass[a4paper,12pt,reqno,twoside]{amsart}
\usepackage{amsmath}
\usepackage{color}
\usepackage{ifpdf}
\usepackage{multirow,bigdelim}
\usepackage{multicol}
\usepackage{tabularx}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\addtolength{\textheight}{2cm}
\addtolength{\topmargin}{-1.5cm}
\addtolength{\textwidth}{2cm}
\addtolength{\oddsidemargin}{-1cm}
\addtolength{\evensidemargin}{-1cm}
\numberwithin{equation}{section}
\newtheorem{definition}{Definition}[section]
\newtheorem{theorem}[definition]{Theorem}
\newtheorem{lemma}[definition]{Lemma}
\newtheorem{proposition}[definition]{Proposition}
\newtheorem{corollary}[definition]{Corollary}
\newtheorem{remark}[definition]{Remark}
\newtheorem{conjecture}[definition]{Conjecture}
\newcommand{\comment}[1]{}
\title[title]%
      {title} 
\author[athor]{author}
%
\date{Version of \today}
%................................
\subjclass[2010]{30D10}
\keywords{Fourier transforms}
%
\AtBeginDocument{%
%\mathtoolsset{showonlyrefs,mathic = true}
\begin{abstract}
abstract
\end{abstract}
\maketitle
%\tableofcontents % Table of Contents
}
%..........................................
\begin{document}
\tableofcontents
\section{test}
The results are listed in the following table.\
This is some text that should appare just before the table.
\begin{table}
    \centering
    \begin{tabularx}{\linewidth}{|c|c|c|L|} 
        \hline
        \textbf{a}&\textbf{b}  &$\boldsymbol{\lambda}$&\textbf{Dynamical equations}  \
        \hline
        &&&$c=d \quad\text{(A)}\quad\quad\text{Hunter-Saxton}$\
        \hline
        0 &b&-1&$a=b \quad\text{(B)}$\
        \hline
        0 &b&1&$c=d \quad\text{(C)}$ \
        \hline
        $a$ &0&$\tfrac12$&$a=b \quad\text{(D)}$ \
        \hline
        $a$ &0&1&$a=b $ \
        \hline
        $a$ &$a$&1&$c=d$ \
        \hline
        $a$ &$\beta a$&1&$c=d$ \
        \hline
        $a$ &$\beta a$&$\lambda$&$a=b$ \
        \hline
    \end{tabularx}
\end{table}
This is some text that should appear just after the table.
\end{document}