Answer: B
Correct answer: a named set of formatting applied to text with one click
A style is a named collection of formatting instructions - font, size, colour, spacing, indentation, borders - that can be applied in one action. Word supplies Normal, Heading 1, Heading 2, Title, Quote and others, and custom styles can be defined. Its value lies in centralised control. Changing the definition of Heading 1 updates every heading using it, however long the document; formatting each heading by hand gives no such link. Styles also carry structure, not just appearance. Applying Heading styles is what allows an automatic table of contents, the Navigation pane, Outline view and collapsible sections to work at all - none of them can detect a heading that has merely been made large and bold. They also make documents accessible, since screen readers use heading levels to navigate. A theme is the related feature that sets fonts and colours document-wide, and a template stores styles for reuse in new documents.