Answer:
The correct answer would be option C, color: blue;
Explanation:
CSS stands for Cascading Style Sheets. It is basically a style sheet language. It describes the presentation of the documents in the markup language. Markup language may include HTML, Java Script, etc.
So when the color of the font is required to change in blue color, the attribute color;blue; would be used to make the color of the font to appear blue in the document.
This language make use of the attributes to present different things in the documents.