A story may explain a reason directly or give a clue through an action. Choose the reason supported by the words rather than inventing an extra event. An inference is an evidence-based idea, not a certainty about every hidden thought.
Worked example
If Ada moves a book away from spilled water, protecting the book is a supported reason. The text does not show that she dislikes reading.
Original fiction: Room on the Bench
Ravi spread his papers over the bench. Ada arrived carrying a heavy model. Ravi quickly stacked his papers and moved them to his bag. "Now your model can sit here," he said. Ada set it down and stretched her arms. They looked at the model together.