The transformation from an assertive sentence to an exclamatory one involves restructuring the sentence to convey strong emotion or emphasis.

The original assertive sentence is: "The moonlight very sweetly sleeps upon this bank."

The correct transformation into an exclamatory sentence is: "How sweetly does the moonlight sleep upon this bank!"

This transformation utilizes the structure of an exclamatory sentence, which typically begins with the word "how" followed by a subject and verb inversion. In this case, "how sweetly" expresses a sense of admiration or wonder at the sweetness of the moonlight's sleep upon the bank. The addition of the exclamation mark emphasizes the emotive nature of the sentence.