Here is the sentence:
Maria knowed the futility of her task that
October afternoon. As she swept off the
front sidewalk, more leaves fell from the
trees overhead, sprinkling the concrete with color.
The first verb, knowed, is the problem. As you know, the sentence requires the simple past. Knew is the correctly spelled form.
| Verb | Simple Present | Simple Past | Past Participle |
| know | know(s) | knew | known |