The correct answer is A. voice-volume.
The voice-volume property sets the volume for spoken content in speech media. It replaces the deprecated volume property.
The volume property sets the volume of all audio elements on a page. It is deprecated in favor of the voice-volume property.
The !important keyword is used to override the default value of a CSS property. It is not used to set the volume of spoken content.
The @media rule is used to specify different CSS styles for different media types. It is not used to set the volume of spoken content.