Which of the following property sets the font size of text?

font
font-text
font-size
none of the mentioned

The correct answer is C. font-size.

The font-size property sets the size of text on an element. It takes a value in pixels, points, or ems. For example, to set the font size of an element to 16px, you would use the following CSS:

font-size: 16px;

The font property is a shorthand property that sets the font family, font style, and font weight of an element. It does not set the font size.

The font-text property is not a valid CSS property.

Therefore, the correct answer is C. font-size.