What does the flexbox model primarily help with?

The flexbox model is designed to facilitate the alignment and distribution of space among items within a container in a more efficient manner compared to traditional layout methods. It provides a flexible way to design responsive layouts that adjust to various screen sizes, making it particularly useful for web developers.

With flexbox, you can easily control the direction, alignment, and spacing of child items within a flex container. For example, you can easily center items vertically and horizontally, distribute space evenly among them, or make them grow and shrink based on the available space. This flexibility significantly enhances the layout capabilities of CSS, allowing for more dynamic and adaptable designs.

The other options don't align with the core functionality of flexbox. While fixed layouts relate to a defined structure and positioning, flexbox is inherently about flexibility and responsiveness. Defining font sizes and styling text elements are aspects more effectively handled by other CSS properties and techniques rather than the flexbox model, which focuses primarily on the layout and arrangement of boxes within a container.