The correct answer is A. background-position-x.
The background-position property defines the initial position of a background image. It takes two values, which represent the horizontal and vertical position of the image, respectively. The horizontal position is defined by the background-position-x property, and the vertical position is defined by the background-position-y property.
For example, the following CSS code will position a background image 10px to the right and 20px from the top of the element:
css
background-position: 10px 20px;
The background-x-axis and background-y-axis properties are not valid CSS properties.