Take a look at the sentence again:
Juan herd his mother calling from down the
street but chose to ignore her summons.
Although he knew that she would be angry
about his late arrival for dinner, he had to finish his inspection of the
dead toad on the sidewalk.
The first verb, herd, is the problem. The sentence requires the simple past. Heard is the correctly spelled form.
| Verb | Simple Present | Simple Past | Past Participle |
| hear | hear(s) | heard | heard |
Knew, the verb you chose, is perfectly correct. Before you continue, review the rules for irregular verbs.
Go back to the sentence to try again.