Take another look at the sentence:

With regret, Jack slung the heavy backpack over his shoulders and fleed the cold library. If he had brought a jacket, he could have continued fantasizing about the cute librarian who sat at the reference desk.

The second verb, fleed, is the problem. The sentence requires the simple past. Fled is the correctly spelled form.

Verb Simple Present Simple Past Past Participle
flee flee(s) fled fled

Slung, the verb you chose, is perfectly correct. Before you continue, review the rules for irregular verbs.

Go back to the sentence to try again.

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