Here is the item:
On Sunday Michael spent the
afternoon waxing his new car. If he had knew
about the two pop quizzes on Monday, he
would have given his algebra
problems and accounting spreadsheets more attention.
The second verb, had knew, is incorrect. As you know, this verb requires the past participle known because of the auxiliary verb had.
Know is an irregular verb; the chart below shows its forms.
| Verb | Simple Present |
Simple Past |
Past Participle |
|---|---|---|---|
| know | know(s) | knew | known |