Review the item:
Tiffany __________ through all of Professor Olefke's 8 a.m. astronomy lectures; at the end of the semester, she would have a better chance escaping the gravity of a black hole than passing the course.

The blank requires the simple past of sleep, an irregular verb. Slept is the simple past form.

Verb Simple
Present
Simple
Past
Past
Participle
sleep sleep(s) slept slept

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

Try again to escape Grammar Hell!