Take another look at the sentence:

While Allison gripped the roof's edge, she no longer resented the many hours that her boyfriend Chris spent in the gym. After all, his strong arms would catch her when she loosened her grip and __________ to the ground below.

The sentence requires the simple past of fall, an irregular verb. Fell is the correct form.

Verb Simple Present Simple Past Past Participle
fall fall(s) fell fallen

Fallen, the form you chose, is a past participle. A past participle requires an auxiliary verb which the sentence does not provide. Before you continue, review the rules for irregular verbs.

Try again to escape Grammar Hell!

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