The correct answer is: C. border-bottom-all
The border-bottom-all property defines in a shorthand form the width, style, and color for the bottom border of an element. It can be used to set all four properties of the bottom border at once, or to override just one or two of them.
The syntax for the border-bottom-all property is as follows:
border-bottom-all: <width> <style> <color>;
The width property specifies the width of the border. The style property specifies the style of the border, such as solid, dashed, or dotted. The color property specifies the color of the border.
For example, the following code will set a solid, 1px black border on the bottom of an element:
border-bottom-all: 1px solid black;
The border-bottom property is similar to the border-bottom-all property, but it only specifies the width and style of the bottom border. The border-bottom-color property only specifies the color of the bottom border.
The none option is not a valid value for the border-bottom property.