Final answer:
Readers make inferences about a character by analyzing their actions, words, and interactions in the text, a process known as characterization.
Step-by-step explanation:
The information primarily used by a reader to make an inference about a character in a story is by using the character's actions, interactions, and words within the text itself. This is known as characterization, which includes the development of characters through their behaviors, descriptions, and dialogue. A character's traits can be reflected in the way they speak or behave, and often authors provide information on the character's background, setting, and other narrative elements to further define them. For inferences in particular, readers look for hints and observed evidence in the text, such as specific word choices or the tone used, to understand the character's nature.