Take a look at the sentence again:
If Carlos had known that hail the size of golf balls would fall later that
day, he would have __________ his shoulder pads and football helmet instead
of his one good suit.
The sentence requires the past participle of wear, an irregular verb. Worn is the past participle form.
| Verb | Simple Present | Simple Past | Past Participle |
| wear | wear(s) | wore | worn |
Wore, the form you chose, is simple past. A simple past verb cannot have auxiliary verbs like would or have. Before you continue, review the rules for irregular verbs.
Try again to escape Grammar Hell!