Here is the sentence:
If Tyree had __________ how beautiful the substitute teacher was going to
be, he would have prepared his math homework—instead of an arsenal of spitballs—to
impress her with his intelligence.
The blank requires the past participle of know, an irregular verb. You chose known, the correct form. Hallelujah!
| Verb | Simple Present | Simple Past | Past Participle |
| know | know(s) | knew | known |