The correct answer is: A. font-size
The font-size property sets the size of the font. It is a length value that specifies the font size in pixels, points, or ems.
The font-variant property specifies the variant of the font. It can be used to set the font to be normal, small-caps, or all-caps.
The font-style property specifies the style of the font. It can be used to set the font to be normal, italic, or oblique.
The font-weight property specifies the weight of the font. It can be used to set the font to be normal, bold, or bolder.