Which of the following describes inline elements in CSS?

Inline elements in CSS are defined by their behavior concerning layout and space. The correct answer indicates that they take up only as much space as their content. This means that inline elements will not break the flow of the content around them; they will only extend as far as necessary to contain their content, allowing text and other inline elements to flow together seamlessly. Examples of inline elements include <span>, <a>, and <em>, which typically display within the block of text without creating a new line before or after them.

The other descriptions do not accurately represent the characteristics of inline elements. For example, specifying width and height applies more to block elements, while the behavior of starting on a new line is typical for block elements, not inline ones. Similarly, inline elements are versatile and used for text styling and inline attributes rather than solely for layout structures. Understanding the behavior of inline elements is crucial for effective web layout and design in CSS.