The correct answer is: A. border-style
The border-style property defines the visual style of up to four different sides of a border. It can be used to specify the border width, border color, and border style for each side of an element.
The border property is a shorthand property that can be used to specify the border width, border color, and border style for all four sides of an element.
The border-top property is used to specify the border width, color, and style for the top border of an element.
The border-bottom property is used to specify the border width, color, and style for the bottom border of an element.
The border-left property is used to specify the border width, color, and style for the left border of an element.
The border-right property is used to specify the border width, color, and style for the right border of an element.
For example, the following CSS code will create a red, 1px solid border around an element:
border: 1px solid red;
The following CSS code will create a red, 1px solid border on the top and bottom of an element, and a blue, 2px dashed border on the left and right sides:
border-top: 1px solid red;
border-bottom: 1px solid red;
border-left: 2px dashed blue;
border-right: 2px dashed blue;