Take another look at the sentence:
Drooling in anticipation of the treat, Sylvia rewarded Gizmo with a dog
cookie.
Drooling in anticipation of the treat, a participle phrase, is right next to Sylvia, an illogical target. The dog, not the owner, should be the one salivating! Before you continue, review the rules for misplaced and dangling modifiers.
Go back to the sentence to try again.