speaking sharply is correct because give a piece of one's mind means to speak angrily or sharply to someone because they have done something wrong.

This idiom or phrase is useful because it helps students understand the intended meaning beyond the individual words.

Examples: The manager gave him a piece of her mind for arriving late every day. My aunt gave me a piece of her mind when I broke my promise.

The idiom involves criticism or anger, not kindness, sadness, or cheerfulness.