Here is the item:
Even though Frances had already ate, she stopped at the food court and bought a slice of pizza. She wanted an opportunity to smile at the cute young man who ran the register.

The first choice, had ate, is incorrect. (Already is an adverb and not officially part of the verb). As you know, this verb requires the past participle eaten because of the auxiliary verb had.

Verb Simple
Present
Simple
Past
Past
Participle
eat eat(s) ate eaten

Go to the next item, champ!