Take another look at the sentence:

When Mr. Tighe saw Julie using Moby-Dick as a coaster for a sweating glass of cold soda, he __________ down his briefcase and lectured the poor young woman on showing proper respect for great literature.

The sentence requires the past tense of throw, an irregular verb. Threw is the simple past form.

Verb Simple Present Simple Past Past Participle
throw throw(s) threw thrown

Throwed, the form you chose, is a spelling error. Before you continue, review the rules for irregular verbs.

Go back to the sentence to try again.