Take another look at the sentence:
Giselle dreaded attending her US Government class. Whenever Dr. Duncan called on her, Giselle felt as if she had __________ in her chair; she couldn't open her mouth, let alone answer one of his questions.
The sentence requires the past participle of freeze, an irregular verb. Frozen is the past participle.
|Verb||Simple Present||Simple Past||Past Participle|
Freezed, the form you chose, is a spelling error. Before you continue, review the rules for irregular verbs.