What should a writer focus on MOST during the revision stage? fixing spelling mistakes
doing new research and adding new ideas
improving how the paper communicates ideas
adding quotes to the paper

improving how the paper communicates ideas--seems most appropriate in the limited context provided.

Explanation:

summary - a brief statement or account of the main points of something.

main idea - the main idea is defined as the main point of a speech or piece of writing.

paragraph - a distinct section of a piece of writing, usually dealing with a single theme and indicated by a new line, indentation, or numbering.