Take a look at the sentence again:
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.