How do I include a jQuery in the body of a content type?
As @Gulok and @Drupalist said it is not good that add your js in content,the simple way to add js with one of below solutions (it is seems you are newbie to drupal I suggest if you want use learn and use drupal  use is correct,I can suggest a solution that you can add js in body(content) but I prefer guide you in correct way ;) )


  The PHP function drupal_add_js() lets you add a JavaScript file,
  setting or inline code to the page and it takes 5 parameters (see the
  api reference).
  
  The first parameter is always going to be a path to a js file, an
  array, or a piece of JavaScript code. If the second parameter is
  'module' (the default), 'theme', or 'core', then the first parameter
  must be a path and the only difference between these three is the
  order in which the script tag will be placed relative to other
  scripts, i.e. core scripts first, then module scripts and finally
  theme scripts.
  
  If the second parameter is 'setting', then the first parameter must be
  an array of settings. This is very handy for telling JavaScript about
  the configuration settings for your module, for example, and is
  explained in more detail in the next section.
  
  The final possibility for the second parameter is "inline" and this
  means you are passing in straight JavaScript code as your first
  parameter, which you want written directly to your page between script
  tags, rather than a call to a file.
  
  These two are the most important parameters for this function - indeed
  you may never even use the second one if all you ever want to do is
  add a js file for your module - but you can learn about the other
  parameters by reading this function's documentation at api.drupal.org.
  Adding JavaScript from within a module
  
  So, let's say you have written some jQuery code that targets some of
  the elements that are output by your module or theme. You simply need
  to save your jQuery code as a JavaScript file (i.e. with the .js
  extension) and place it in your module or theme's directory. If it's
  for a module, you then need to make the call to drupal_add_js() as
  above, from wherever the module is about to output content (e.g. in
  hook_block or hook_nodeapi), or if the JS is not acting on content
  output by your own module you can call it from hook_menu or hook_init.
  Note, that putting this file into hook_init means it will run on every
  page request, whether needed or not. Here is how you would ensure the
  file gets added:
  
  
  
  The jquery.js file is included automatically so you don't need to
  worry about adding it.
  
  To add JS (or CSS) file from form builder function the recommended way
  is to use Form API #attached property as below,
  
  
  
  See Form API reference for more details. Adding JavaScript from within
  a theme
  
  Adding JavaScript to a Drupal 8 theme With drupal_add_js (Drupal 6 &amp;
  7)
  
  (drupal_add_js is deprecated in Drupal 8; use '#attached' instead.) If
  you are adding your .js file from within a theme, then you simply need
  to make the call from within template.php, you need to add the second
  parameter this time as 'theme' so that Drupal knows this script should
  be loaded after all core and module scripts are loaded:

  &lt;?php drupal_add_js(drupal_get_path('theme', 'mytheme')   .'/mytheme.js'); ?&gt;

  
  Using the theme's .info file (Drupal 6 &amp; 7)
  
  You can add your script path in the .info file of your theme and
  Drupal will include them automatically. name = My theme description =
  Theme developed by me. core = 7.x engine = phptemplate

     scripts[] = mytheme.js Using a preprocess_page function

  
  To conditionally add js to the theme, you can use a process_page
  function:


 &lt;?php function mytheme_preprocess_page(&amp;$vars, $hook) {   if (true) {
     drupal_add_js(drupal_get_path('theme', 'mytheme') . '/mytheme.js');
     $vars['scripts'] = drupal_get_js(); // necessary in D7?   } } ?&gt;


and according you comment your js will be something like 

I try to include a jQuery in the body of a content type, as shown in the image below:

enter image description here

The purpose of this jQuery is to hide a div with id="test", so that the text aaaaaaaaaaaaaaaaaaaa in it is not shown.

The jQuery was added to the content (saved in it), but yet I still can see the aaaaaaaaaaaaaaaaaaaa and my js did not run.

Seems like Drupal JQuery.js file is not loaded, so how can I get it loaded?

(function($) {
$(document).ready(function(){
$('#wrap').hide();
});
})(jQuery);