the headings and subheadings of the body of an outline should be __________. long parallel interesting complicated
Thea headings and subheadings of the body of an outline should be parallel.
They don't really have to be long and complicated, and of course, interesting.
I believe the answer is: Parallel
Here is an example of parallel placement:
HEADING
SUBHEADING
The purpose of such arrangement is to ensure that the readers understand that the information that written in the subheading is a part of the heading as a whole. Also, from aesthetical point of view it make the writing become much more convenient to read.