Take a look at the sentence again:
At the video arcade, Jeremy wished that he had
slew the giant mutant tomatoes on level one. Then he
would not have fought the kamikaze pickles
on level two and could have kept his grape
bombs for the ninja carrots on level three.
The first verb, had slew, is the problem. This verb requires the past participle. Had slain is the correct verb.
| Verb | Simple Present | Simple Past | Past Participle |
| slay | slay(s) | slew | slain |
Could have kept, the verb you chose, is perfectly correct. Before you continue, review the rules for irregular verbs.
Go back to the sentence to try again.