Answer:
as textual evidence
Explanation:
When making a summary of a story's key events to write about a story's theme, one can use the summary as a textual evidence because the key events of the story would would be used as evidence to back up the claims for the theme of the story.
For example, if the theme of a story is supposedly "greed", then the key events that would be used to show the theme would be called a textual evidence.
