What is the CSS property used for adjusting the size of text?

The property used for adjusting the size of text in CSS is the font-size property. This property allows developers to specify the size of the text, which directly impacts how text appears on a webpage. By using font-size, you can set values in various units, including pixels (px), ems, rems, percentages, and points, providing flexibility in design.

For example, if you want larger text for headings or smaller text for footnotes, font-size can be adjusted accordingly to achieve the desired visual hierarchy and readability. This makes it essential for ensuring that text is appropriately sized for different devices and screen resolutions, enhancing the user experience.

Other properties mentioned in the choices serve different purposes. Text-align adjusts the horizontal alignment of text within an element, font-family specifies the typeface used for the text, and line-height controls the spacing between lines of text. However, none of these properties affect the actual size of the text itself, making font-size the correct choice for this particular question.