In the Foundations of Verbal, one of the drills is to determine whether the sentence has an error and to identify the adverb.

"The performer danced lively, delighting the children."

This was marked as an incorrect sentence, but all they explained was that "lively" was an adjective, not an adverb, so it cannot be correct. Why is "lively" not an adverb? Doesn't it describe danced which is a verb?