What aspect of design is primarily concerned with the readability of text?

The correct choice, typography, focuses on the design of text and its presentation, which plays a crucial role in establishing readability. Typography encompasses several elements, including font type, size, spacing, and line length, all of which impact how easily text can be read. Well-executed typography enhances legibility and ensures that the text communicates its message effectively, making it a fundamental aspect of graphic design.

In contrast, while alignment refers to the arrangement of text and graphics relative to one another, and hierarchy involves organizing elements to guide the viewer's attention, neither directly affects the inherent readability of the text itself. Similarly, contrast deals with the visual differences between elements, such as light and dark or different colors, which can enhance readability but does not encompass the full scope of how text is designed and viewed. Therefore, typography is the most accurate answer, as it specifically addresses the design choices that influence how readable the text is.