Review the item:
Using bites of bologna as bribes, Diane convinced Reliable, her beagle, to lie still, and then she __________ each of his eighteen toenails.

The blank requires the simple past of cut, an irregular verb that never changes form. Cut is the simple past.

Verb Simple
Present
Simple
Past
Past
Participle
cut cut(s) cut cut

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

Try again to escape Grammar Hell!