First of all, version 1.1 of the API has been deprecated for quite some time now. Users are strongly encouraged to move their applications over to version 2.1.
The URL for retrieving information about a question looks something like this:
For example, to retrieve information about this very question, one would visit:
As you have already noted, this does not include the actual post body. Version 2.0 of the API introduced the concept of filters, which (in your case) requires that you manually specify that you would like to fetch the post body.
Normally you would need to create the filter yourself, but since all you want is the post body, you can use one of the predefined filters:
Your URL now becomes: