What is the primary purpose of cascading style sheets (CSS)?

Cascading Style Sheets (CSS) primarily serve the purpose of describing how HTML elements should be displayed on a web page. This includes defining the layout, colors, fonts, spacing, and overall visual aesthetics of the web content. By separating content (HTML) from presentation (CSS), web developers can create a more organized and maintainable structure, allowing for consistent styling across multiple pages.

The design flexibility provided by CSS enables developers to apply styles seamlessly throughout an entire website, making it easy to update the appearance without altering the underlying HTML structure. This separation also enhances responsiveness, where CSS can be used to make web applications adaptable to various screen sizes and devices.

While interactive web applications and client-server communication are essential components of web development, they are handled by different technologies such as JavaScript for interactivity and server-side languages for data management. CSS focuses specifically on presentation, making option B the most relevant and accurate answer regarding the purpose of CSS.