The correct answer is: A. radial-gradient()
A radial gradient is a type of CSS gradient that creates a smooth transition between two or more colors. It is created using the radial-gradient() function, which takes the following syntax:
radial-gradient(circle at <position>, <start-color> [, <end-color> [, <stops>]])
The circle keyword specifies that the gradient should be circular in shape. The at keyword specifies the position of the center of the gradient. The start-color and end-color keywords specify the colors of the start and end of the gradient, respectively. The stops keyword specifies the locations of the color stops, which are points along the gradient where the color changes.
For example, the following CSS code creates a radial gradient that starts with red at the center and fades to blue at the edge:
background-image: radial-gradient(circle at 50% 50%, red, blue);
The elliptical-gradient() function is similar to the radial-gradient() function, but it creates an elliptical gradient instead of a circular gradient. The elliptical-gradient() function takes the same syntax as the radial-gradient() function, except that the circle keyword is replaced with the ellipse keyword.
The none of the mentioned option is incorrect because it does not specify a valid CSS gradient function.