Sweetly means doing something in a manner that is sweet in taste.

• A. Sweetly
• B. Bitterly
• C. Sourly
• D. Saltily

Answer: (A)

This question tests choosing the adverb that expresses sweetness in how something is done. Sweetly means in a sweet manner or with a sweet taste, so it exactly matches the idea of performing an action in a way that is sweet in taste. The other words describe other taste qualities—bitterly for bitterness, sourly for sourness, and saltily for saltiness—which would not convey sweetness. Therefore, the best choice is the one that literally communicates sweetness in manner.